MOSCOW, JULY 16 -- The Ukraine formally proclaimed its sovereignty within the Soviet Union today, saying that it plans to become a neutral state with its own armed forces, citizenship laws and currency.

The declaration of autonomy by the Soviet republic's legislature is significant not only because of the Ukraine's size and importance, but also because it goes much further than steps taken by other non-Baltic Soviet republics that have asserted their sovereignty. With a population of more than 51 million, the Ukraine is the second-largest of the Soviet Union's 15 constituent republics and produces 25 percent of the country's food and coal and 20 percent of its gross industrial output.

So far, only the tiny Baltic republics -- Lithuania, Estonia and Latvia -- have adopted more radical sovereignty declarations than the Ukraine, asserting their full independence from Moscow. But those three have never been regarded as integral parts of the Soviet Union's Slavic heartland, historically made up of Russia, the Ukraine and Byelorussia.

The Ukrainian legislature, meeting in Kiev, asserted the supremacy of its authority within the republic over that of the Soviet Union and repudiated the production, use and spread of nuclear arms there.

The immediate effect of the Ukrainian declaration -- and those of a number of other Soviet republics in recent months, is unclear. For the moment, they appear to have largely symbolic value as each republic prepares its position for talks on the future of a politically reorganized Soviet Union. The Ukraine could not fully enforce its economic claims without Kremlin cooperation.

As the Ukrainian legislature adopted its declaration, the official Soviet news agency Tass reported tension along the border between the Soviet Central Asian republics of Kirghizia and Uzbekistan. About 30 people were reported injured in the west Kirghizian city of Osh in renewed clashes between Uzbeks and Kirghiz. Similar clashes sparked by a land dispute between the two ethnic groups in early June left 148 dead and nearly 900 injured.

The Ukraine is the 10th Soviet republic to assert the primacy of its own laws over those of the Soviet Union. The only republics that have not yet passed such declarations are conservative Byelorussia and most of the Moslem republics of Central Asia, where political developments have traditionally lagged behind the rest of the country.

Tass reported that while the vote for the declaration in the Ukrainian legislature was nearly unanimous, most of the speakers at the session opposed outright secession from the Soviet Union. There is a lively independence movement in the Ukraine, but it is centered on the western region around Lvov that was not annexed by the Soviet Union until 1940, under terms of a non-aggression pact with Nazi Germany.

According to Tass, the Ukrainian declaration asserted the republic's right to "have its own armed forces, interior troops and state security bodies." It also insisted that Ukrainian citizens serving in the Soviet army should not be deployed outside the republic without permission from the Ukrainian legislature.

The document also proclaimed the Ukraine's intention to become "a constantly neutral state, not participating in military blocs and adhering to three principles -- not to produce, not to spread, and not to use nuclear weapons." It did not set a date for achievement of this goal.

The nuclear issue is an extremely sensitive one in the Ukraine, which suffered serious radioactive pollution following the fire and radiation eruption at the Chernobyl nuclear power plant in 1986. Official counts put the death toll from the accident at 31, but an independent group this year counted more than 300 deaths resulting from the incident. More than 116,000 people were relocated from the region, vast areas of the republic have been declared an ecological disaster area, and local farms are still subject to restrictions on livestock.

The Ukraine, like Byelorussia, already has its own seat at the United Nations, awarded to the republic after World War II as a political concession to Soviet dictator Joseph Stalin by the Western powers. The Ukrainian delegate to the United Nations has always slavishly adhered to the line laid down by Moscow.

In an attempt to defuse growing demands by the Soviet republics for a greater say in running their own affairs, Gorbachev has called for renegotiation of the 1922 treaty of union that established the Soviet Union. Both the Ukraine and the Russian republic, under populist President Boris Yeltsin, are likely to play key roles in negotiation of a new treaty.

The Ukrainian nationalist movement Rukh has formed an opposition coalition in the Ukrainian legislature with dissident Communists and ecologists. The sovereignty declaration was adopted by a 355 to 4 vote, an indication of how far the official Communist majority in the legislature has had to move in order to keep pace with the pressure from Rukh.

The main issue dividing the two sides was a proposed law on Ukrainian citizenship, one of Rukh's main demands. In the end, the legislature adopted a compromise, allowing for dual Ukrainian and Soviet citizenship.