MOSCOW, JULY 28 -- The presidents of the three Soviet Baltic republics declared in a joint statement today that they will not take part in planned negotiations toward making the Soviet Union a looser confederation of semiautonomous republics and will continue to press for absolute independence from Moscow.

The declaration came at the conclusion of a two-day meeting of the three Baltic leaders at the Latvian coastal city of Jurmala and followed discussions there with Russian President Boris Yeltsin, who agreed Friday to bypass the Kremlin and negotiate sovereign treaties on mutual relations between Russia and the Baltics, Latvian news media reported.

In today's statement, the Baltic leaders said they "consider it impossible" to participate in work on the new treaty of union among the Soviet republics, and said "it would be best" if their negotiations with Moscow "were held on the basis of the three-plus-one principle" -- that is, the three Baltic republics plus the Soviet government.

The statement was signed by presidents Arnold Ruutel of Estonia, Anatoly Gorbunovs of Latvia and Vytautas Landsbergis of Lithuania, which is scheduled to begin separate talks on independence with the Kremlin in the next week or two.

A new treaty redefining the relationship of the Soviet Union's 15 constituent republics has been in preparation since early this year and is widely viewed as an urgent attempt by Soviet President Mikhail Gorbachev to hold the country's diverse and restive republics together as the Soviet Union undergoes unprecedented political and economic change. Gorbachev said last week, however, that the Kremlin would have to retain control of eight key public sectors, including the military, currency, energy and transport.

Already, 11 republics have unilaterally declared varying degrees of autonomy within the Soviet system, the latest being the key western republic of Byelorussia, which on Friday, like the neighboring Ukraine, asserted its right to become a neutral, nuclear-free state with its own armed forces and banking system.

Lithuania declared outright independence on March 11, and both Latvia and Estonia have declared their intention to follow at the end of unspecified transition periods. The Kremlin reacted to Lithuania's claim by imposing a tight energy embargo on the republic, which was lifted late last month when the Lithuanian legislature agreed to suspend its proclamation of independence in return for formal talks with the Kremlin about a negotiated secession.

In their statement today, the Baltic presidents said relations between their formerly independent republics and Moscow should be governed by treaties signed before 1940, when all three republics were forcibly incorporated into the Soviet Union as a result of a pre-World War II agreement between the Soviets and Nazi Germany.

A Soviet spokesman said last week that a draft of the new treaty of union would probably be ready for final approval by December.