This is the CBS Sunday Night News, Bill Plant reporting. Good evening. Plenty of posturing and positioning as Israeli and Arab leaders prepare for a historic Mideast Peace Conference this week. Chief European correspondent Tom Fenton sets the scene for us tonight from Madrid. The eyes of the world will be on the Spanish royal palace this Wednesday. In the ornate former ballroom, the Israelis and Arabs will break the ice of a stalemate that has lasted almost half a century. The very act of sitting down together will have tremendous symbolic importance. Palestinians and their far-off refugee camps will be following every move in Madrid, looking for a ray of hope and fearing a sellout. All sides have taken the hardest possible positions in advance, knowing that only a compromise can produce any progress. The Spaniards have taken on an awesome responsibility, including a security problem complicated by the fact that the nature of the conference makes every participant a potential assassin's target. But it's the United States that is assuming the greatest risk in this historic opportunity. If the conference leads to eventual peace, it could be the crowning achievement in President Bush's New World Order. But if it fails, the United States will reap the hate of another generation of Arabs. Tom Fenton, CBS News, Madrid. Israelis remain upset with Palestinians who are publicly linking their delegation to the Palestine Liberation Organization. Bert Quinn has more in Tel Aviv. The pre-conference routine of threat and counter-threat intensified today, with Palestinians and Israelis warning each other they might walk away from the peace talks. The PLO, which officially isn't supposed to be at the conference, but boasts of its control over the Palestinian delegates, said it might order the Palestinians to walk out of the conference if the Israelis didn't stop building settlements in the occupied territories. And the Israelis, at today's cabinet meeting, said they will walk out if the Palestinians declare publicly in Madrid that they take orders from the PLO. As for the conference itself, the Israelis sounded as adamant as ever about not giving up any of the land they conquered from the Arabs during the 1967 war. But one minister spoke of Jews and Arabs facing each other across a table. The very fact that we are sitting means that we are not fighting, and this is a great deal. Despite the threats and the rhetoric, the door to peace at least is being unlocked. Bert Quinn, CBS News, Tel Aviv. The amazing thing about the Middle East peace conference is that it's happening at all. It's a product of the end of the Cold War and the outcome of the Gulf War. And even then, it took Secretary of State Baker and the administration eight months of cajoling and shuttle diplomacy to get Israel, Syria, Jordan, Lebanon, and the Palestinians to agree to sit down together. The parties are coming to the table not so much because they want to make peace with each other, say yes to each other, but because they don't want to say no to the United States. There's a lot to talk about, ending the state of war between Syria and Israel, a secure border between Israel and Lebanon, and eventually about normal relations between Israel and all the Arab states of the region. Then there's the Palestinian question. As the U.S. keeps insisting, the Palestinians of all the players at the table may have the most to gain. It's a terribly important moment symbolically and politically and culturally because we have been a suppressed voice for long. And it's one area where most observers believe the Israelis may be ready to make concessions. I think there there is a considerable chance that some of the meaner aspects of the occupation will in time lessen. Beyond that, the idea of a Palestinian state, self-determination, I think that's still a ways away. Difficult questions, but the U.S. is counting on the pressures which brought everyone to Madrid to keep them talking and keep them from walking. The Soviet Union, formerly the Arab state's main patron, is a co-sponsor of this week's peace conference, an opportunity for Mikhail Gorbachev to return to the world stage. Jonathan Sanders reports from Moscow. Mikhail Gorbachev leaves tomorrow for Madrid to assume a favorite role, world statesman. But his home base, the Soviet Union, has changed immeasurably since the last time he ventured abroad. The Kremlin now plays from weakness, not strength. This weekend, another Soviet republic, Turkmenia, declared its independence from Moscow. There are many centers of power in this formerly monolithic country. It's increasingly unclear just whom Gorbachev represents. He no longer represents the Arabs. Last week, Israel reopened its Moscow embassy as the Kremlin resumed diplomatic relations after a quarter century of Mideast policy based on anti-Zionism. Since now the Soviet Union has diplomatic relations with Israel, it can be a little more even-handed than it was in the past. President Gorbachev has another agenda on this trip. He'll meet President Bush and later in France, President Mitterrand. He's expected to push his case for Western economic aid. Soviets say the West should not worry about another coup in Gorbachev's first trip away from Moscow since August. The country, they say, is too preoccupied with figuring out how to survive the winter. Jonathan Sanders, CBS News, Moscow. Still ahead on the CBS Sunday night news, the family of hostage Terry Anderson marks his birthday. Happy birthday to you. 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President Lech Walesa and millions of other Poles headed to the voting booth today in the first open parliamentary election since 1947. In Yugoslavia, federal troops are tightening their noose around the Croatian stronghold of Dubrovnik. One Croatian official says the four-month-old civil war has claimed 5,000 lives so far. Pictures taken inside Croatia in recent weeks show just how brutal the war has become. Martha Teichner has that story. When Croat fighters recaptured their village from Serbian invaders, they returned to a massacre. A 91-year-old grandmother was found clinging to her 76-year-old friend. Both were shot in the chest. A 22-year-old policeman who was beaten and then shot in the back. 24 inhabitants of the tiny community of Cetakovac were slaughtered simply because they were Croats. Milan Buterot said the killers wore masks, but he recognized them as people he had known all his life from the Serb village just down the road. The Serbs say the Cetakovac massacre was in retaliation for killings by Croats in another village. This spiral of revenge had its origins in the atrocities committed by both sides during World War II. With each funeral, an old wound is reopened, providing its own excuse to fester on for generations to come. Martha Teichner, CBS News, London. The First United Nations Ceasefire observers are due to arrive in Cambodia tomorrow. Their arrival comes less than a week after the government and opposition groups signed their peace treaty in Paris. I just can't stand this anymore. How am I supposed to fall asleep with this pain? I could take one of those nighttime pain relievers with a sleep ingredient. But all I really need is Advil to help stop the pain that's keeping me up. Just Advil. That's all I want. I want the extra sleep ingredient I don't want. Advil is so effective, it relieves the pain so I can get to sleep. Discover the relief of Advil at bedtime. Advil, advanced medicine for pain. Once again, Buick is raising the banner for quality in America, introducing the 1992 Les Sabres with a higher level of power, safety, security, and convenience. This new Les Sabres is going to be one tough act to follow. Les Sabres for 1992 from Buick. Forecasters are predicting more stormy weather for North Texas, where heavy rains have caused severe flooding. Those floods are being blamed for two deaths. As much as seven inches of rain fell last night in the Dallas-Fort Worth area. A deadly freak accident has prompted environmental artist Christo to dismantle his display of giant umbrellas. Gusting winds in the mountains above Los Angeles, yesterday blew one of the 485 pound umbrellas across a road, crushing a woman against a boulder. Christo had planted more than 3,000 of the umbrellas on hillsides in California and Japan. The White House is growing increasingly concerned with the political fallout from the sluggish economy. Randall Pinkston at the White House has that report. President Bush and his top advisors continue to trade charges with Democrats over the best solution to the nation's economic crisis. Treasury Secretary Nicholas Brady attacked the Democrats' proposal for a middle income tax cut. Not a single Democratic person has come forward with a program that doesn't either bust the budget agreement or raise taxes. House Speaker Foley in turn attacked the White House proposal for a reduction in the capital gains tax. To talk about a tax break as the President does for this top bracket, this richest group in the country, while ignoring the pleas and problems of the middle income bracket, simply not fair. But there are signs that the two sides may be coming together. The White House, for example, has not completely ruled out the Democrats' proposal to give middle income taxpayers a break. It doesn't mean that if we can get a middle income tax cut that fits within the budget agreement that it shouldn't be looked at. Still, the Bush administration views a middle income tax cut as a less desirable option than a package of proposals already sent to Congress, including a cut in the capital gains tax, tax credits for research and development projects, and a highway bill slowly winding its way through Capitol Hill. Whatever the final result, no tax break is likely before the end of the year. Randall Pinkston, CBS News, The White House. Finally, today was Terry Anderson's 44th birthday, his seventh in captivity. His relatives marked the occasion with a church service. His sister, Peggy Say, said she is optimistic that he will be released soon, and she fully expects to spend Christmas with her brother this year. That's the CBS Sunday Night News. I'm Bill Plant in New York. Good night and have a good week.