European allies and NATO welcomed President George W. Bush's willingness to cooperate in his plans for a nuclear missile shield outlined on Tuesday, while Russia hoped Washington would not ditch an existing 1972 arms treaty.
Both Bush's allies and Russia, a bitter opponent with China of any U.S. anti-missile shield, welcomed the U.S. president's accompanying offer of unilateral arms cuts.
Officials in Moscow warned of a new arms race if Washington abandoned the nearly three-decades-old Anti-Ballistic Missile (ABM) treaty, which Bush said he wanted replaced.
But they appeared hopeful Bush would not unilaterally ditch what has been a bedrock of U.S.-Russian nuclear stability.
U.N. Secretary-General Kofi Annan also made clear he hoped the treaty would not be scrapped.
China stressed in a report on Bush's speech on the missile defence system by its official Xinhua news agency that Beijing was "hostile" to it.
It quoted analysts as saying such a system "will not only spark a new arms race...but will also threaten world peace and security in the 21st century".
NATO Secretary-General George Robertson welcomed Bush's commitment to consult closely with allies on the anti-missile defence scheme, which Washington says would protect the United States and its allies from attack from so-called "rogue nations" or accidental nuclear launches.
"The president is right to focus on these new challenges, and I welcome his commitment to close consultation with the allies," Robertson said in a statement.
Britain said it supported Bush's commitment to cut nuclear weapons and welcomed his contacts with Russia to explain Washington's controversial plans to replace the ABM treaty.
"I welcome the president's commitment to reductions in U.S. nuclear weapons," British Foreign Secretary Robin Cook said in a statement. "It is good news that President Bush spoke to (Russian) President (Vladimir) Putin today."
Bush phoned Putin on Tuesday to explain his missile plans, and said he wanted to meet the Russian leader before a Group of Eight summit this summer.
Several Western states are deeply concerned about the U.S. plan for a missile defence system which some fear could disrupt the arms status quo between former Cold War foes.
French President Jacques Chirac has called it an "invitation to proliferation".
But Britain has voiced sympathy for the proposals. Its support could be crucial, because the United States may require permission to upgrade radar facilities in northern England.
Reflecting Russia's reaction to Bush's speech, Interfax news agency quoted what it called "military-diplomatic sources" as welcoming the president's offer of unilateral nuclear arms cuts.
"Moscow has received signals from Washington that there are forces in the American administration which understand the negative consequences of the United States taking unilateral decisions about leaving ABM and deploying a national missile defence system," Interfax quoted the sources as saying.
"Many in Washington understand that the destruction of ABM and deploying an anti-missile shield could undermine the system of strategic stability which exists in the world today and lead to a new arms race," the sources added.
U.N. chief Annan, stressing the importance of existing arms treaties, said through a spokesman that he "believes that in promoting respect for the rule of law in international affairs, there is a need to consolidate and build upon existing disarmament and non-proliferation agreements".
"In this context, the secretary-general appeals to all states to engage in negotiations towards legally binding disarmament agreements that are both verifiable and irreversible."
Canada also urged Washington not to tear up the ABM treaty. Foreign Minister John Manley said Ottawa feared Washington could trigger an arms race if it did so.
"We have made a number of points very clear to the United States in the various discussions we've had. Number one is that we think a unilateral abrogation of the ABM would be very problematic for us," Manley told reporters.