WASHINGTON -- The United States and European leaders indicated less concern yesterday about the future name or shape of the Soviet Union than about who would control the nuclear arsenal spread over four republics.
Giving a cautious welcome to the new structure supplanting the Soviet Union, Washington stressed its hope that the old superpower's nuclear arsenal be kept under "a single, unified control."
White House and State Department spokesmen said they were encouraged that the communique issued by the leaders of Russia, Ukraine and Byelarus establishing their Commonwealth of Independent States addressed concerns raised by the United States over the transformation of the Soviet Union.
Their response indicated that fears of a violent breakup like the one in Yugoslavia, which were raised Sunday by Secretary of State James A. Baker III, had been at least partly allayed.
Most of the nuclear stockpile is in the three newly joined republics.
The reaction from the United States followed its pattern, set when Ukrainians voted for independence Dec. 1, of accepting even radical changes in the former Soviet Union provided they occur peacefully.
"To date, there has been a peaceful transformation of this gigantic, complex situation. This is very comforting to us," said State Department spokeswoman Margaret D. Tutwiler. "They appear, by the facts, to be working out their own transformation, as they should, evolving as they decide to in a peaceful manner."
Byelarussian officials are to meet today with a top Baker aide.
U.S. officials took with equanimity the fact that, as one put it, Soviet President Mikhail S. Gorbachev is left with "no more than a possible symbolic role." There was no official U.S. comment on his negative reaction to formation of the commonwealth, but a senior official said, "What's important is how is it viewed in his own country."
But officials continued to register concern over control of nuclear weapons.
"We support a single, unified control over the nuclear weapons in theSoviet Union, wherever they are. We do not want to see a proliferation of independent nuclear states," Ms. Tutwiler said. But she said the United States was not insisting that all of the weapons be moved to Russia.
The new commonwealth does not include Kazakhstan, which has nuclear weapons. Mr. Baker might include the Central Asian republic on his trip to Russia, Ukraine and Byelarus starting late this week.
In Maastricht, Netherlands, European Community leaders announced that they were sending an envoy to Russia, Ukraine and Byelarus to seek guarantees that arms control accords signed by the Soviet government will be honored.
"In order to have a safe world, we do need certain undertakings as to how the people holding those nuclear weapons behave," said British Foreign Secretary Douglas Hurd.
Ukrainian President Leonid Kravchuk said yesterday that the three members of the new alliance would exercise a "triple control" over nuclear weapons. "This black box can be activated only when three buttons are pressed at the same time," he said at a news conference. "All this enhances control of nuclear forces."
Bruce Blair, a Brookings Institution expert on Soviet command and control of nuclear weapons, said yesterday that the republics with nuclear weapons appeared to be moving toward sharing control of the nuclear trigger with Mr. Gorbachev and toward veto power by one or more republican leaders over a nuclear attack.
Such an arrangement, he said, would offer "less and less opportunity for a single person to order the use of nuclear weapons," providing the West with additional safeguards.
But disintegration of central institutions, including the military, and the chance of a right-wing coup threaten the cohesion of these emerging arrangements, he said.
Mr. Blair also noted that Russia has the only large disposal site for nuclear warheads. Ukraine and other republics have been unwilling to allow their nuclear forces to be brought back to Russia for destruction.