"Such steps must not hurt Russia's security interests," said Russian Foreign Minister Igor Ivanov while on a visit to Tokyo, the Interfax news agency reported.

"Such a move must also not prompt a new arms race," Interfax quoted Ivanov as saying.

Ivanov's comments were terser than the Russian foreign ministry statement, released earlier Wednesday in Moscow.

"Moscow views with regret the renewal of US efforts to create a so-called global missile defense system," the Russian foreign ministry said in the statement, Moscow's first reaction to Bush's Tuesday announcement.

Following through on one of his main presidential campaign pledges, Bush on Tuesday said the United States would field a limited missile defense shield by 2004.

US officials said the blueprint called for 10 ground-based interceptor missiles at Fort Greeley in Alaska by 2004 and another 10 interceptors by 2005 or 2006.

Defense Secretary Donald Rumsfeld acknowledged the system will be deployed before it is fully developed, but that by 2005 it will be able to intercept a "relatively small number of incoming ballistic missiles."

Differences over missile defense framed a tense US-Russian relationship prior to the September 11, 2001 attacks on US cities, which then prompted Russian President Vladimir Putin to offer warm support for a global "anti-terror" campaign.

That new partnership was sealed at a May summit in Moscow at which Bush and Putin vowed to slash the two sides' nuclear arsenals by two thirds over a 10-year span.

But the treaty implicitly allowed the United States to push ahead with missile shield development, even as Russia voiced hope that Bush would change his mind following the launch of war in Afghanistan.

More spending on missile defense along with the threat that other countries would boost their own missile spending to counter the new US shield threatened to "drain resources from fighting today's real threats -- first of all, international terrorism," the Moscow statement warned.

Igor Sergeyev, a former defense minister who serves as Putin's advisor on strategic defense, argued Wednesday that Washington has failed to assure Moscow that the shield was aimed against nations like North Korea rather than Russia itself.

"We cannot fail but notice that the shield is being unfurled not in the south -- where the perceived danger from so-called rogue states is coming from -- but in the north," the direction from which Russian missile could rain down on US soil, said Sergeyev.

Meanwhile lawmakers in Russia's State Duma lower house of parliament -- which must still ratify the May disarmament treaty -- launched a move to amend the May disarmament agreement to let Russia withdraw from the pact under "exceptional circumstances."

The proposed new amendments would allow Moscow to pull out of the pact should Russia feel threatened by the US missile shield, especially if it is transformed into an offensive space-based program further down the line.

Duma defense committee chairman Andrei Nikolayev said he would propose that US or NATO military decisions threatening Russia's national security, and serious Russian economic difficulties, would allow Russia to abandon the pact and keep its nuclear arms.

Nikolayev did not say when the deputies would examine the proposed amendments.