The Soviet Union is moving some tactical nuclear weapons from domestic storage depots in outlying areas of the country marked by ethnic conflict and nationalist tensions and storing them in the Russian republic, in a consolidation of weaponry aimed partly at safeguarding the warheads from unauthorized capture, U.S. officials confirmed yesterday.

The officials said they did not know the number of nuclear weapons moved into the Russian republic from remote depots in the northern Baltic states and strife-torn areas south of the Caucasus Mountains. They said Soviet officials had recently informed U.S. government officials and independent experts only in general terms that the arms were being relocated to safer areas.

"They are finally doing the right thing," said a senior U.S. official, who explained that movement of the short-range arms will substantially reduce what Washington believes is a fairly remote possibility that the nuclear arms could fall into the hands of terrorists or renegade groups. He and others confirmed a report yesterday in the Wall Street Journal that the weaponry was being moved.

Soviet President Mikhail Gorbachev is engaged in a struggle with leaders in Latvia, Estonia and Lithuania over their republics' moves to independence, leaving the ultimate disposition of extensive military facilities and weapons storage depots there uncertain.

Soviet officials have told Westerners that they became concerned about the fate of nuclear weapons stored near the Soviet border with Turkey and Iran due to the continuing conflict between Azerbaijani and Armenian populations in the Transcaucasus region, which has led to clashes with military forces and thefts of conventional arms from government stockpiles.

"This is a reflection of the fact that the Soviets are bracing themselves for long-term turmoil in these areas and are trying to avoid even the remotest possibility of an incident," a U.S. official said.

Soviet Foreign Minister Eduard Shevardnadze signaled high-level concern when he warned several months ago in an extraordinary Moscow speech that "no one can calculate the consequences of a social explosion capable of igniting . . . the giant stockpiles of nuclear and chemical weapons and nuclear power stations" in regions "shaken by inter-ethnic strife."

Joint Chiefs of Staff Chairman Gen. Colin L. Powell said at the National Press Club yesterday, however, that he is not worried about the possibility of an unauthorized nuclear detonation in the Soviet Union.

"Obviously, we all are interested in the control that the Soviet Union is able to continue exercising over their very large nuclear arsenal," Powell said. "Our concern is heightened by what's been happening in some of the republics of the Soviet Union.

"The one thing I would like to say, though, is that based on my knowledge of how the Soviets manage their nuclear systems and the kind of safeguards they have for their nuclear systems, I'm fairly comfortable that those weapons will not get into improper hands, or even if they were able to, the systems they have to protect those weapons would make them pretty much unusable," Powell said.

Powell was referring to equipment that evidently prevents Soviet nuclear weapons from being armed without proper authorization or after being accelerated or spun, which normally arms the warhead when fired from a launcher in wartime.

Soviet Maj. Gen. Geli Batenin, a military expert of the Communist Party's Central Committee, told the official Novosti press agency recently that these "electronic code and mechanical blocking" devices could be "lifted only by . . . the president."