Russia has pledged widespread cuts in its arsenal
Russian Foreign Ministry spokesman Alexander Yakovenko said arms reductions agreed between the two sides last year should be "irreversible" and not just "on paper".
He was speaking after a Pentagon planner said on Wednesday that some of the weapons which President George W Bush pledged to cut would be kept in reserve.
The US said it needed to keep weapons in reserve in case of "unforeseen international events".
It was the second time this week that Russia has criticised US nuclear policy, currently undergoing a top-level review.
On Wednesday Russia stressed its support for a ban on nuclear testing after US newspapers reported that the Bush administration was considering lifting its moratorium on tests.
Safety fears
White House spokesman Ari Fleischer said President Bush had "not ruled out testing in the future, but there are no plans to do so".
The US argues it will need to resume testing to check the safety of its arsenal, especially as weapons get older.
In November, Moscow and Washington agreed parallel reductions in their nuclear warheads, although nothing was laid out in a formal treaty.
On Wednesday Mr Yakovenko said Russia now wants the reductions to be "radical", "controllable" and "irreversible".
The BBC's Stephen Dalziel says this latest message from Moscow seems to make clear that the new mood of co-operation between Russia and the US in the fight against terrorism does not mean an end to serious disagreements.
Tit-for-tat
Washington has already upset Moscow by announcing its withdrawal from the 1972 Anti-Ballistic Missile Treaty in order to press ahead with a new missile defence programme.
But that decision seemed to have been tempered by the proposal - agreed by presidents George Bush and Vladimir Putin during the latter's visit to the US in November - that sweeping cuts would be made in nuclear arsenals.
Mr Bush said the US would cut back over the next 10 years from its current total of some 7,000 warheads to about 2,000.
Mr Putin said that if the US were to do this, Russia would follow suit, cutting down from some 6,000 to about 1,500.
Mr Bush's national security adviser, Condoleezza Rice, subsequently hinted that the US might opt for storage of warheads, rather than destruction.
On Wednesday, Washington made its plans clearer.
"Some [weapons] will be removed from operations status and earmarked for destruction," said White House spokesman Ari Fleischer.
"Others will be placed in retirement for status for eventual destruction and others will be maintained in a non-deployment status as a hedge against unforeseen technical international events," he said.
However, Mr Putin is keen to scrap warheads which are expensive to maintain as part of a wider plan to reform the armed forces.
Our correspondent says that if the Americans are not scrapping the warheads, the Russian military will see unilateral destruction by Moscow as a sign of weakness.