OSCOW, March 11 — Defense Minister Sergei B. Ivanov of Russia warned today that the American proposal in arms reduction talks to "warehouse" excess warheads instead of destroying them would not only encourage nuclear proliferation, but could even set off a new kind of arms race.

Mr. Ivanov's statement, in written answers to questions from The New York Times, was issued as he flew to Washington for four days of talks on arms control, terrorism and other issues. It underscored the fact that despite hopes of sealing a major arms reduction agreement by late May, when President Bush plans to visit Moscow, the two sides remain at loggerheads as to what arms reduction actually means.

Russian negotiators, who propose cutting their nuclear force to as few as 1,500 warheads, insist that any excess warheads be destroyed, along with launch vehicles and other essentials. That was the practice in every previous nuclear arms reduction accord.

The Bush administration has said it wants to reduce the 6,000-warhead arsenal of the United States to between 1,700 and 2,200 warheads. But it intends to keep an unspecified share of those excess warheads and their carriers in storage, ready for retrieval in a matter of weeks or months if necessary.

Today, Mr. Ivanov said Russian policy "is based on the irreversibility of the reduction of strategic weapons." The American proposal — to store the warheads, and retrofit some idled missiles and planes with high-precision conventional bombs — is unacceptable, he said.

"Can such a reduction be considered a real one? Make your own judgment," Mr. Ivanov said today. "If, at a certain point, the United States considers the situation to be taking an `unfavorable turn,' then within several weeks, months or years the number of operationally deployed warheads may be restored to the desired level."

He maintained that other nations would feel compelled to warehouse their own nuclear weapons for emergencies, worsening the problem of controlling nuclear arms stocks. He also predicted that the American plan would start a new kind of arms race by forcing other nations — presumably, Russia — to develop speedier methods of restoring idled nuclear weapons to battle readiness.

The Kremlin echoed Mr. Ivanov's sober view of the nuclear arms situation today by officially condemning a leaked Pentagon report that includes Russia among seven nations identified as plausible targets for American nuclear strikes. The report, a periodic review of nuclear strategy, focuses largely on the need to deter or defeat nations like Iraq that are thought to be developing weapons of mass destruction that could be used in regional wars against American allies or as terrorist weapons.

The report's authors conclude that while relations with Russia have dramatically improved, the United States should make contingencies for an unanticipated reversal that could revive cold war hostilities.

Today the Russian foreign minister, Igor S. Ivanov, called on the Bush administration to explain the report. His spokesman, Aleksandr Yakovenko, told reporters it remained to be seen "to what point this information corresponds to reality.

"If it does, how can you reconcile it with declarations of the United States that it no longer considers Russia as an enemy?" he said.

After two days of silence, China's government also issued a statement saying it was "deeply shocked" by newspaper reports that it, too, was among the seven nations labeled potential targets. The classified analysis identified Beijing as a potentially hostile power with an expanding nuclear force, and speculated that the United States could respond with nuclear weapons should China launch an attack on Taiwan.

The spokesman for China's Foreign Ministry, Sun Yuxi, demanded an explanation of the report, saying the United States and China had long agreed not to regard each other as targets for nuclear arms.

He also stressed China's opposition to using or threatening to use nuclear weapons against a non-nuclear nation, an underlying theme of the Pentagon report. The report discusses at length the possibility of using small nuclear arms on precise targets to wipe out chemical or biological weapons sites in locations like underground bunkers that are invulnerable to ordinary bombs.

One rationale for considering this possibility is that chemical and biological weapons can be as devastating as nuclear ones, and that the United States might have no choice were it faced with clear evidence that such arms were about to be used against its citizens.

American officials have strongly defended the Pentagon analysis, saying it is a duty of military planners to prepare for any conceivable war. While the document outlines potential nuclear strategies, they say, it does not change American policy and does not imply that any of the nations mentioned have in fact been made nuclear targets.

At least one ally, Germany, weighed in with a similar assessment today, perhaps to blunt criticism in Germany itself of a Social Democratic-Greens government that is facing a tough election campaign this year and has allied itself with the Bush administration's war on terrorism, despite criticism from the left wing. "There are no U.S. plans for attack. That is an exaggeration that does not correspond with reality," said the government's spokesman, Uwe-Karsten Heye.