What perestroika giveth ...

MIKHAIL GORBACHEV wanted the Baltics to be a showcase for perestroika, a place where restructuring is working. And by Soviet standards the three small republics have done well. But a loosened grip by the Kremlin freed up more than productivity; it also unleashed nationalistic feelings that have simmered in Estonia, Latvia, and Lithuania ever since they were absorbed into the Soviet Union a half-century ago.

Political rumblings for autonomy have reverberations in Armenia, Soviet Georgia, the Ukraine, Central Asia, and other parts of Mr. Gorbachev's sprawling domain. The violent conflict between the Armenian and Azerbaijani republics has flared again in the last few days, resulting in 18 deaths, by the latest reports.

The Soviet leader feels these tremors as he rushes to complete a rebuilding of his country's political structure - a structure designed to consolidate executive authority and give real power to the legislature. The Communist Party's Central Committee has given its OK to the plan, and the Supreme Soviet - the country's current rubber-stamp national legislature - followed its lead yesterday. In a remarkable break with the past, however, five delegates voted against parts of the Gorbachev package, and 27 abstained. All the dissenters were from the Baltics.

Gorbachev sees his efforts as crucial, giving him the ability to cut through bureaucratic sludge and carry out reform, and giving the Soviet people a taste of democracy through elective bodies with genuine policymaking authority. Others, such as Andrei Sakharov, have warned that the ultimate result could be the opposite of democracy - a dictatorial executive who accumulates power instead of sharing it. The country's ingrained, repressive political culture gives that dark vision credence.

The Estonians, joined by the Armenians and the Georgians, are worried about centralization, too. They see Gorbachev's plan as an encroachment on the rights of their republics.

Under the Soviet Constitution, those rights have been extensive - on paper. They include the right to secede. Of course no republic has ever been allowed to exercise these rights, though Estonia seemed to be putting them to the test with its recent declaration of sovereignty.

Gorbachev declared that declaration ``totally unacceptable.'' He took particular exception to the Estonians' effort to revive private property, making clear that such an idea is still heresy in the cradle of communism. Gorbachev's speech to the Supreme Soviet, however, took a conciliatory approach, offering the republics greater representation in the new lawmaking apparatus and putting some legislative restraints on his new presidential powers.

The Baltic nationalists were undeterred. Lithuanian President Vitautas Astrauskas proclaimed, ``We are tired of living under orders from above.'' The Estonian party leader, Vaino Valjas, asserted, ``We will not retreat.''

Under present circumstances, it's hard to know which direction is a retreat. The constitutional changes being pushed by Gorbachev may do away with the hollow powers now accorded republics, but they may end up giving republics more actual autonomy over their economic destinies. Politics is another matter. It's doubtful anything like the kind of quasi-independence desired by the Estonians will be allowed.

Reformers in the Baltics have pursued their path of separate development under the banner of perestroika. Gorbachev puts forth his plan for a revamped government under the same banner - yet his goals and the Estonians' are colliding.

The Estonians, unfortunately, may be about to learn that what perestroika giveth, it can also take away.