WASHINGTON (Reuters) - German Foreign Minister Joschka Fischer said on Wednesday he did not expect the United States to withdraw suddenly from a Soviet-era pact with Moscow called the Anti-Ballistic Missile Treaty (ABM).

``I'm not pessimistic about that. I don't want to say more,'' Fischer told reporters at the German ambassador's residence on the third and final day of a trip to the United States.

President George W. Bush said before he was elected in 2000 that he would build an anti-missile shield to protect all U.S. territory and possibly that of its allies against missile attack, even if it meant withdrawing from ABM, which specifically prohibits building such a system.

Moscow and Beijing oppose Bush's plans for the system, called National Missile Defense (NMD), fearing it would neutralize their defenses.

Fischer was speaking a day after meeting Vice President Dick Cheney, Secretary of State Colin Powell and National Security Advisor Condoleezza Rice. He had been asked if there was a risk Washington would pull out precipitously from ABM.

Signed in 1972, the pact is seen as the cornerstone of arms control by many countries but Defense Secretary Donald Rumsfeld dismissed it in December 2000 as ``ancient history.''

It allowed the Soviet Union and the United States to place missiles on their own territory to protect their capital cities and one other site from attack by other missiles.

The Clinton administration, sharing the view that emerging post-Cold War threats required a new defense, tried to no avail to persuade Moscow to agree to amend the ABM treaty.

Fischer's comment, made amid remarks that focused on his discussions with Powell, indicated the new secretary of state had reassured him the United States would not do anything rash with regard to ABM, which Moscow wants to keep intact.

But German officials traveling with Fischer declined to give any details of the substance of his talks on Tuesday with Cheney and Rice, or to say whether they took place in such a constructive an atmosphere as those with Powell.

German diplomats heaped praise on Powell's approach, stressing he was ``not at all gung-ho'' on NMD, or other issues including U.S.-British air strikes against Iraq last week.

Fischer, who visited Moscow this month, said he believed the U.S. administration was ready for a debate on NMD, and that there was a chance for constructive debate with Russia.

After his talks with Powell on Tuesday, he said they had a ''very good discussion'' on NMD, adding, ``We are looking forward to a close consultation within NATO and on a bilateral level.''

Fischer also met U.S. trade representative Robert Zoellick and was due to return to Berlin on Wednesday.

Republicans regard ABM as irrelevant to U.S. interests in the post-Cold War era, arguing that new threats from what they call ''rogue states'' including North Korea, Iran and Iraq require a new defensive posture by the United States.

The Bush administration has never said it will negotiate with Russia on amending the ABM, though it has stressed it will consult its European allies, and Russia and China.

Powell has said there will be ample time to consult others during what is bound to be a lengthy process of testing NMD technology, which is still at early stages of development.

Critics say the shield, at a possible cost of $60 billion, would prompt other countries to amass more nuclear weapons.