THE breakup of the Soviet Union has caused a row among independence-minded republics over representation in the diplomatic corps and in international organizations.The Soviet Union and the republics of the Ukraine and Byelorussia already have seats in the United Nations. During the 46th General Assembly session, which opens today, the newly independent Baltic states - Lithuania, Latvia, and Estonia - also will be seated. Lithuanian President Vytautas Landsbergis and the Ukrainian parliament chairman, Leonid Kravchuk, are scheduled to address the Assembly. Many of the remaining Soviet republics are complaining they do not have a proper voice at the UN, and even the republics with representation are not entirely satisfied. The source of much discontent is the declarations of independence adopted by 11 of the 15 republics after last month's failed hard-liner coup. "There are attempts by the center to make the Ukraine follow their policies," said Alexander Yemets, chairman of the Ukrainian parliament's Human Rights Commission. "The Ukraine is independent and will use its seat at the UN in an independent manner." The Ukraine and Byelorussia gained membership in the UN under former dictator Joseph Stalin. Fearing Western attempts to dominate the UN during its formation after World War II, Stalin originally wanted all 15 republics to be represented but settled for the three seats. To help settle disputes, Foreign Minister Boris Pankin met with leaders of nine republics Friday, agreeing to form a Council of Foreign Ministers to coordinate policy. Yuri Zorin, deputy mission head at the Central Asian republic of Uzbekistan's delegation in Moscow, called the meeting a positive development, but added that more progress is needed. Only two Uzbeks sit in the 56 Soviet trade missions in foreign countries to which Uzkbekistan exports products, he notes. The Ukraine was noticeably absent at Friday's meeting. Mr. Yemets said the problem of representation will only be settled once the central authorities understand their role in the new Union of Sovereign Republics. Mr. Pankin has said that while the 15 republics should have international representation, membership in key bodies, such as the UN Security Council, should be retained by the Soviet Union. Yemets called that unrealistic. "We think the Union as a state doesn't have a future, while the Ukraine does," Yemets said. "The center has the opposite opinion."