CNN founder Ted Turner and former senator Sam Nunn (D-Ga.) yesterday formally unveiled plans for a Washington-based nonprofit organization that will focus on safeguarding nuclear weapons and fissile materials in the former Soviet Union.

Turner, a media billionaire and philanthropist who has already pledged to donate $1 billion to the United Nations, said he would give $250 million to the so-called Nuclear Threat Initiative over the next five years because nuclear weapons represent "the greatest threat humanity faces" in the short term.

"Despite the fact that we are no longer enemies, the U.S. and Russia still maintain nearly 3,000 nuclear weapons each on high alert," Turner said at the National Press Club. "An accidental exchange is not out of the question. In many ways, the threat has become more complex and dangerous."

While noting that he personally favors the "complete elimination of all weapons of mass destruction," Turner said the Nuclear Threat Initiative would pursue "pragmatic and effective steps" to reduce the threat.

Turner and Nunn will be co-chairmen of the organization. Its 11-member board of directors includes two senators, Pete V. Domenici (R-N.M.) and Richard G. Lugar (R-Ind.). "I'm just one voice in deciding how the money is distributed," Turner said.

Nunn, who will also serve as the organization's chief executive, ran down a long list of possible projects for the new group, from funding nongovernmental organizations to aiding the families of underpaid Russian scientists who formerly produced nuclear, chemical and biological weapons.

One immediate focus, Nunn said, would be to help consolidate fissile materials in the former Soviet Union so that they can be properly safeguarded. "There is tremendous vulnerability to theft and terrorism and illegal sales," Nunn said, adding that Russian scientists "are in great demand by terrorist groups, but don't know how to feed their families."

Nunn said the organization also could serve as a venture capital fund in the former Soviet Union while contributing several million dollars a year to accelerating U.S. programs for converting weapons-grade uranium and plutonium to commercial uses.

"There is a gap between the threat and the response, and we're going to try to help . . . as much as we possibly can," said Nunn, who served as chairman of the Senate Armed Services Committee before retiring in 1996. "Fifty million dollars a year sounds like an awful lot of money, but in the sea of challenges out there in this arena, this is small potatoes. But I think we can come in where there are niches, and we can be a catalyst."

Nunn said the U.S. government clearly can do better on nonproliferation issues, and he challenged President-elect Bush to reexamine America's entire nuclear posture, including the Comprehensive Nuclear Test Ban Treaty, which the Senate rejected in 1999.

Nunn said the United States has done more than any other government to help safeguard nuclear weapons and fissile materials in the former Soviet Union, calling on America's NATO allies and Japan to do far more.

Nunn said two foreign experts in the field have agreed to join the Nuclear Threat Initiative's board -- former Swedish ambassador Rolf Ekeus, who headed the U.N. Special Commission in Iraq from 1991 to 1997, and Andrei Kokoshin, Russia's former first deputy defense minister who now serves in the Russian parliament.

Another board member, former deputy secretary of energy Charles Curtis, will serve as the organization's chief operating officer.