President Bush yesterday sharply condemned the Soviet government's use of lethal force in Lithuania and declared the action "could not help but affect" the partnership he has forged with Moscow to supplant the longstanding enmity between the two nations.

Returning to the White House from Camp David, a somber Bush called on "the Soviet leaders" to refrain from further violence, which has led to 13 deaths in the Lithuanian capital of Vilnius. Asked by a reporter if he feared Soviet President Mikhail Gorbachev had "lost control" of Soviet security forces, Bush said only that he was concerned about "the internal affairs there."

Administration officials said the central mystery, which they will seek to clear up before deciding whether to take punitive steps against the Soviet Union, is if and to what extent the crackdown was ordered by Gorbachev.

Officials said another key question is whether the military takeover of local institutions in Lithuania will also occur in the other Soviet Baltic republics, Latvia and Estonia, which like Lithuania have declared independence from the Soviet Union. A U.S. official said last night such a move seems likely in Latvia and possible in Estonia.

U.S. Ambassador Jack Matlock was called to the Soviet Foreign Ministry yesterday and given what one Washington official called "an obscure and limp explanation" for the bloody events in Vilnius. An attempt will be made today to get an explanation from Gorbachev about his view of and role in the crackdown before Bush decides on new statements or actions, an official said.

Initially, sanctions against the Soviet Union are likely to be limited to the economic sphere, such as suspension of the credit guarantees approved last month for Soviet purchases of up to $1 billion worth of U.S. commodities. Asked if the summit scheduled for next month might be canceled, Bush said yesterday the question was "too hypothetical." Any steps taken by the United States probably will be coordinated with U.S. allies in Western Europe. The political committee of the North Atlantic alliance met twice yesterday to discuss the Baltic situation.

A senior official on the aircraft of Secretary of State James A. Baker III, who was on the final part of a diplomatic journey related to the crisis in the Persian Gulf, said no decision has been made to postpone or cancel the Moscow summit.

Washington Post staff writer David Hoffman, who is traveling with Baker, quoted that official as saying that for the time being, "we are expressing serious concern, we are characterizing these events as tragic, as moving the Soviet Union in the wrong direction, moving us in the wrong direction {but} we are not at this stage announcing specific measures we might or might not have to take."

The official also said that "there are still, in my opinion, areas where it is to the mutual advantage of both countries to continue to try and work things out," specifically citing arms control.

Both Bush and Baker publicly warned that the shift in U.S.-Soviet relations from the antagonism that prevailed since the end of World War II to cooperation in international affairs was imperiled.

Democratic and peaceful change in the Soviet Union has "helped to create a basis for unprecedented cooperation and partnership" but the events in Lithuania "are completely inconsistent with that course," Bush said. Moreover, the unjustified use of force against democratically elected governments threatens "to set back or perhaps even reverse the process of reform which is so important in the world in the development of the new international order," Bush added.

The president said he did not believe the developments in the Baltic states jeopardized Soviet support for the United Nations resolutions demanding that Iraq withdraw from Kuwait, and that Gorbachev had assured him in a telephone conversation Friday that his support for the U.N. approach "is solid and firm."

The Baltic situation was discussed only briefly between the two presidents in the Friday call, according to Bush. Bush discussed it at least briefly with Soviet Ambassador Alexander Bessmertnykh in his two visits to the White House Friday, and it was discussed at greater length and intensity with Bessmertnykh by national security adviser Brent Scowcroft, according to U.S. sources.

The presentation made by the Soviet Foreign Ministry to Matlock in Moscow included assurances that all human rights guaranteed by the Helsinki Final Act, to which the Soviet Union is a signatory, are being respected in the Baltic states. But a U.S. diplomat in Washington said that representation "doesn't correspond with what is going on."

An administration official familiar with the events said Lithuania was "almost a textbook case" of crackdowns on democratic movements that were executed by Moscow in pre-Gorbachev times. He referred to the organization of a "national salvation committee" to demand military intervention and the takeover of key buildings, including mass communication facilities.

It seems unlikely that such an extensive and well-prepared operation could take place without the approval of Gorbachev, the highest political authority of both the government and Communist Party, several officials said. However, some officials cited the possibility that Gorbachev gave a general approval for the crackdown, which then either went beyond what he expected or spun out of control.

As evidence of Gorbachev's involvement, officials cited a tough message sent in his name to the Lithuanian Supreme Council, or legislature, last Thursday charging the breakaway republic with "implementing a policy aimed at restoring a bourgeois system" and calling for "urgent measures" to accept rule from Moscow.

If the suppression of Baltic governments continues unabated, the drive toward the rule of law in the Soviet Union as well as the popularly elected governments in other Soviet republics and major cities, including Moscow and Leningrad, may be at risk, an administration official said.

There were some reports that reformist elements in Moscow and in the republics were seeking to rally to reverse the crackdown, official sources said. The probable effect of any punitive steps on the Soviet internal situation, especially that in the republics, will be considered by the United States and its allies in deciding their reaction, an official said.

One Soviet watcher in the administration admitted to "a sinking feeling," triggered by fears that the crackdown in Vilnius could be the start of a sequence of events leading to the ouster or resignation of Gorbachev. He emphasized that this is his personal view, not an official assessment.

Scowcroft, on NBC's "Meet the Press," likened the Soviet action in Lithuania to Moscow's suppression of the Hungarian revolution in 1956, which took place during a Middle East crisis over the Suez Canal. In the same way, the current Soviet crackdown has been overshadowed in recent days by the impending United Nations deadline for Iraqi withdrawal from Kuwait that could result in the United States and its allies going to war against Iraq.