The Senate yesterday unanimously approved a treaty to slash U.S. and Russian nuclear weapons deployments by two-thirds over the next decade, another milestone in the disarming of two powers that once threatened each other with horrific attacks. The vote was 95 to 0.

The treaty, signed last year in Moscow by President Bush and Russian President Vladimir Putin and awaiting approval by the Russian parliament, calls on each nation to reduce deployments of strategic, or long-range, weapons to between 1,700 and 2,200 weapons by the year 2012 -- their lowest level since the 1950s.

The pact does not require the actual destruction of the weapons, leading some senators, especially Democrats, to question whether stockpiled Russian weapons might fall into the hands of terrorists or rogue countries.

Bush has hailed the Moscow Treaty as strengthening ties between the former Cold War rivals. The administration pushed for swift approval at a time when it is seeking to persuade Russia not to block a new United Nations resolution paving the way for military action against Iraq.

"As important as the substance is, it is the form -- the trust between the United States and Russia -- that shines through," said Majority Leader Bill Frist (R-Tenn.). It may not be perfect, but it is "an important step toward a safer world," said Foreign Relations Committee Chairman Richard G. Lugar (R-Ind.).

Over the years, the Senate has approved a series of arms control agreements with the former Soviet Union, although its record on international weapons pacts is mixed. Most recently, it approved a chemical weapons ban but rejected a treaty to ban nuclear weapons testing.

Most of the two-day Senate debate over the three-page pact, which omitted many of the details and complexities that characterized far longer Cold War-era agreements, centered on what was not in it rather than what was. While Democrats said they supported the treaty as a step forward in U.S.-Russian relations, they said it lacks verification requirements, enforcement provisions, mechanisms for weapons destruction or timetables for interim deadlines.

At the end of the process, both countries will have no fewer weapons at their disposal than they have now, said Sen. Byron L. Dorgan (D-N.D.). "I guess it's fine to have an agreement for the sake of agreement, but for what value?" he asked.

Sen. Joseph R. Biden Jr. (Del.), ranking Democrat on the Foreign Relations Committee, said he was concerned that Russia lacks the financial resources to protect its mothballed stockpiles of nuclear weapons, exposing them to possible theft or clandestine sale to hostile individuals or nations. He called for greater funding of the Nunn-Lugar program of assistance for the destruction of Russian weapons of mass destruction.

Later, Biden joined Minority Leader Thomas A. Daschle (S.D.), Sen. Joseph I. Lieberman (Conn.) and other Democrats in proposing a separate resolution assailing the administration's actions on weapons proliferation and outlining proposals of their own. The resolution, which did not come to a vote, urged the administration to start building an anti-proliferation coalition, to engage North Korea to deter it from pursuing its nuclear weapons program, to increase funding for nuclear security programs and to put more resources into homeland security.

In one of the few votes on amendments, which Senate leaders had discouraged, a proposal to require Senate notification before the United States could withdraw from the treaty was rejected, 44 to 50. Another to require annual intelligence reports on compliance was defeated, 45 to 50.

Sen. Dianne Feinstein (D-Calif.) said Bush should act shortly after the pact is ratified to reduce the high-alert status of U.S. nuclear arsenals and urge Putin to follow suit. Recalling a 1995 incident in which the Russian military initially interpreted the launch of a U.S. weather rocket as a possible nuclear attack, she said the high-alert status means weapons are ready to be launched at a moment's notice, and are thus vulnerable to mistakes or sabotage.