The House has approved legislation calling for exchange visits between the U.S. nuclear test site in Nevada and Russia's test site on an Arctic archipelago in an effort to promote openness in the face of reported signs Russia may be preparing to resume nuclear testing.

Rep. Curt Weldon, R-Pa., who sponsored the amendment, told the House last week that a classified intelligence briefing for certain members of Congress had included information on possible "new movement in the area of nuclear weapons and nuclear materials."

The New York Times reported on its Web site Saturday that classified briefings for select House and Senate members included information on a new analysis by the Joint Atomic Energy Intelligence Committee indicating that Moscow is preparing to resume testing at the Novaya Zemlya testing area. The committee gathers views from different federal agencies on nuclear issues.

Weldon said in a statement his amendment was designed to promote safety, security and transparency with Russia by encouraging joint nonproliferation and threat-reduction efforts.

The amendment also reverses a ban on scientific research to develop nuclear weapons that can defeat chemical and biological weapon production and storage facilities.

"No president should have their hands tied by outdated laws that stifle research and development into new technologies that will safeguard us in the future," Weldon said. "The fact is, our adversaries are developing chemical and biological weapons that pose a significant threat to America and our allies."

The new questions about Russia's nuclear testing come just weeks before President Bush is to meet with Russian President Vladimir Putin for a May 23-26 summit in Russia where arms control is on the agenda.

Russia has observed a moratorium on full-scale nuclear testing since its last test explosion in October 1990.

Moscow has said it would continue to conduct subcritical test blasts that are not prohibited by the international Comprehensive Test Ban Treaty because they are necessary to ensure the safety of the country's nuclear arsenal. In subcritical experiments, plutonium is blasted with explosives too weak to set off an atomic explosion.

Critics warn that carrying out even limited tests could encourage other countries to conduct full-scale nuclear tests.

Russia ratified the test ban treaty in May 2000. The treaty was signed by President Clinton in 1996. Bush has said he does not support the treaty and will not ask the Senate to approve it, but will not violate it.

The Weldon proposal was approved 362-53 as an amendment to legislation that passed the House on Friday authorizing $383 billion in national security spending during the 2003 budget year. A House-Senate conference committee will work out differences between differing bills approved by the two chambers.

The CIA, State Department and White House had no comment on reports that Russia may be preparing to resume testing.