It's in our nation's best interest to work with Russia to dismantle its nuclear arsenal

President Bush

The announcement of the review comes hard on the heels of a tit-for-tat spying row in which each country expelled 50 of the other's diplomats.

Last month US authorities arrested Robert Hansen, an alleged spy for Moscow who worked for the Federal Bureau of Investigation.

Ties have been further strained by the proposed sales of Russian nuclear technology to Iran and US determination to build its national missile defence system.

Unease

Part of getting tough with the Russians is cutting back on these programmes, which is absolutely foolhardy

Joseph Biden, Democrat senator

Washington spends more than $1bn a year helping Russia dismantle former Soviet weapons of mass destruction and preventing those arms and their designers from falling into "rogue" hands.

News of the review prompted alarm in the US Congress.

"They think we're going to get tough with the Russians, and part of getting tough with the Russians is cutting back on these programmes, which is absolutely foolhardy," said Senator Joseph Biden, top Democrat on the Senate Foreign Relations Committee.

Mr Bush, however, played down fears.

Robert Hanssen could face the death penalty if convicted

"We're reviewing all programmes� related to de-escalating potential nuclear problems," he told a news conference in Washington.

"We fully intend to continue to cooperate with the Russians."

Earlier the New York Times, quoting an unnamed senior administration official, said the review was likely to result in a significant alteration to the amount of aid extended.

Iran links

Mr Bush said last week that he thought he could have a "good working" relationship with Moscow.

His officials say they are watching Russian developments closely, following an extensive cabinet reshuffle in which President Putin replaced his controversial nuclear energy minister, Yevgeny Adamov.

"Putin and company assure us that Russia intends to stand by its non-proliferation commitments, and yet we see an Atomic Energy Ministry that we think has been tolerating - if not supporting - transfers of sensitive technology to Iran," a senior State Department official told the AFP news agency.