WHEN Lebanon accepted an invitation to attend the Middle East peace conference that opens in Madrid Oct. 30, it did so with minimal enthusiasm.Most Lebanese are greatly concerned that their interests will be submerged beneath the wider Arab-Israeli problem. In line with all the other Arab parties to the conference, Lebanon is insisting that the main purpose should be to secure an Israeli withdrawal from occupied land. Since 1985, Israel has imposed a nine-mile-deep "security zone" in southern Lebanon. To keep its demands from being overshadowed, the Beirut government has sought and received assurances from United States Secretary of State James Baker III. These were contained in a letter accompanying the invitation to the Madrid talks. "The letter stresses Washington's commitment to Lebanon's territorial integrity within its internationally recognized borders," a senior Lebanese official said, "and respects our demand that Israel's withdrawal from the south be treated as an issue separate from the others." Lebanon is well aware that the main focus of the Middle East peace conference will be on United Nations Resolutions 242 and 338 - which relate to the Israeli occupation of the West Bank, Gaza Strip, and Golan Heights. But Lebanese interest is in Resolution 425, which demands complete and immediate withdrawal of Israeli forces from southern Lebanon. But some see a fundamental difference in emphasis between Resolutions 425 and 242. "Resolution 242 has more than one interpretation," argues Fida Nasrallah, a research associate at the Center for Lebanese Studies at Oxford, "and what is required of the conference is agreement whether Israel should withdraw from all of the occupied territories or from some of them. Resolution 425, on the other hand, is quite clear. It does not need any international conference to interpret it, it only requires implementation." The Beirut government argues that while the delineation of borders between Israel on the one side and Jordan and Syria on the other may be subject to dispute, the Israeli-Lebanese frontier is clear-cut. It was defined by the 1949 Armistice Agreement which is still binding. The reality, though, is that Lebanon's demand can not be viewed in isolation from the wider Middle East scene. Lebanon is linked by wide-ranging treaties of cooperation to its powerful eastern neighbor Syria. The Damascus government is gaining an increasingly tight grip on all aspects of life in Lebanon - not least on the policies of the government. Not all Lebanese, both inside and outside the government, are happy attending the conference, but they feel they have no option. Not to attend would risk being excluded from a forum where decisions affecting Lebanon are being taken. In any case, Syria has insisted on Lebanon's attendance. Earlier this month President Elias Hrawi and President Hafez al-Assad met in Damascus to work out a common approach to the Madrid conference. "I think it is safe to assume that Assad did all the talking," a Western diplomat in the Syrian capital commented. President Assad is determined to resist Israeli pressure to make the withdrawal from southern Lebanon conditional on the pull-out of Syrian forces. About 40,000 Syrian troops are deployed in Lebanon. Damascus argues that their presence is regulated by an agreement between Lebanon and Syria - while the Israelis are an occupying force. Abdel-Wahab Baderkhan, a political commentator writing in the London daily Al-Hayat, points out that Lebanon cannot ignore the interests of other parties within its borders. "The difficult question remains - whether or not the recovery of southern Lebanon from Israel will be of any benefit to Syrian interests on the path to a Middle East settlement." Beirut diplomats feel that Syria's prime concern is the recovery of the Golan Heights. Unless some trade-off happens to involve the withdrawal of Israeli troops from Lebanon, the demands of the Beirut government will have to wait their turn. "Lebanon will not be speaking with its own voice at Madrid," one Western envoy said. "Syria will tell it what to say - that's the price of the 'Pax Syriana Ms. Nasrallah believes that while Washington has given Syria a free hand to sort out Lebanon's internal problems, the question of the south will eventually be the subject of a US-Israeli agreement. "Lebanon," she concludes, "finds itself once again the primary loser in this game of 'musical chairs' in the Middle East."