WASHINGTON - Russia is pulling out of a program that poured $1 billion from the US government and other foreign donors into the research labs that built the Soviet Union's vast arsenal of weapons of mass destruction.

Officials with the International Science and Technology Center are negotiating to close the Moscow headquarters of the organization, which was formed in 1994, three years after the Soviet Union collapsed. The center gave tens of thousands of experts in nuclear, chemical and biological warfare the chance to engage in civilian research and work with colleagues from the US and other nations that once stood on the other side of the Iron Curtain.

The program helped pay the salaries of Russian weapons scientists, but it long outlived the crisis that inspired its creation. Russia came to regard the intergovernmental program as obsolete as the country's economy surged over the past decade.

Russia's US ambassador, Sergey Kislyak, who negotiated the establishment of the center, told The Associated Press that his country no longer needs it. "The mission has been accomplished," he said. "It is a little bit outdated."

US congressional investigators concluded that US taxpayer money helped Russia's weapons institutes stay in business by recruiting younger scientists and retaining key personnel who might otherwise have moved to the West _ a finding at odds with the program's goal of reducing the threat of weapons of mass destruction.

Foreign aid programs helped keep Russia afloat as it lurched from crisis to crisis in the 1990s. But the Kremlin has been phasing these programs out in recent years, saying in effect it no longer needs to be treated as a charity case.

In August, Russian President Dmitry Medvedev's office issued a brief statement announcing Russia's withdrawal from the program in six months. The center's director, Adriaan van der Meer, said he is negotiating the terms of the closure and hopes to win an agreement for "an orderly wind down" over the next several years of 355 Russian projects worth about $155 million.

Van der Meer said the center will continue working in Ukraine, Georgia, Belarus and several Central Asian states, where it runs about $95 million worth of projects. Over the past 17 years, the center has tracked space debris, developed fusion power, searched for vaccines against deadly diseases like Ebola and much more.

When the program began after the collapse of the Soviet Union, the Russian economy was in shambles and the government struggled to pay salaries in secret cities where armies of technicians, engineers and scientists designed and built weapons.

"It really provided a lifeline in the 1990s for people who were underpaid or underemployed and might otherwise have gotten desperate enough to sell their services elsewhere," said Matthew Bunn of Harvard University's Belfer Center for Science and International Affairs.

Today Russia pumps more oil than Saudi Arabia, holds almost $500 billion in currency reserves and by one measure has the world's seventh-largest economy. Increasingly, the Russian government has regarded foreign aid as an embarrassing reminder of its past dependence on aid. But some arms control experts said Russia's decision may also have been motivated by security concerns.

Retired US Army Brig. Gen. Kevin Ryan, executive director for research at the Belfer Center, said that both Russia's Federal Security Service and the FBI have long worried that Russian and US weapons scientists working together on peaceful projects might inadvertently spill state secrets. "That's the risk for everybody, but they consider it a higher risk than we do," Ryan said.

The US contributes about one-third of the money for the center's projects, van der Meer said, while the European Union pays for another third, and Canada, Norway, Japan and South Korea the rest.

Arms control advocates such as Ryan say the program still plays a vital role by supplementing salaries at underfunded weapons institutes and fostering ties between Russian and Western scientists.

A 2007 Government Accountability Office study of US Energy Department collaborative research programs in Russia found that senior officials at many former Soviet labs believed there was no longer any need for Western financial support.

Lab officials in Russia and Ukraine told the GAO, Congress' investigative arm, that foreign grants had helped them recruit and retain key personnel, preventing them from emigrating to the United States or other advanced industrial nations. These officials told the GAO that there was "little danger of scientists migrating to countries of concern," according to the 2007 study.

The center was prohibited from funding weapons work: The point was to introduce weapons scientists to civilian research. Congress objected when it discovered in 2008 that some of the institutes receiving US aid were also working with Iran's nuclear program, specifically the recently completed nuclear power plant at Bushehr. The US has long contended that Iranian officials use the Bushehr civilian power project as cover for pursuing a nuclear weapons program. Iran has always denied it is seeking to build atomic weapons.

Relations between the US and Russia have roller coastered since the center opened in 1994, reaching a high point after the September 2001 terrorist attacks and a post-Cold War low in the aftermath of the August 2008 war between Georgia and Russia.

Under the Obama administration's reset of ties with Russia, Moscow has agreed to let the US ship military supplies to Afghanistan through its territory, supported tough new UN sanctions against Iran and signed the New START treaty reducing the ceiling on both countries' nuclear arsenals.

Despite these improvements, US intelligence officials say Russia remains wary of US intentions. "Russian military programs are driven largely by Moscow's perception that the United States and NATO are Russia's principal strategic challenges and greatest potential threat," James Clapper, director of national intelligence, told Congress in March.

Russia has recently launched a $700 billion drive to modernize its nuclear and conventional military forces by 2020.

Henry Sokolski, who once served as the Pentagon's deputy for nonproliferation policy and is now director of the Nonproliferation Policy Education Center, a Washington-based nonprofit, said the International Science and Technology Center leaves a mixed legacy. "Whatever good it might have done to deflect weapons activities, it probably undid by supporting these institutes, which  in "closed cities" that didn't appear on any maps. Van der Meer and several US officials said they hoped the center's programs could continue in some form in Russia.

"It would be very silly to destroy the investment of over $1 billion over the years," van der Meer said.