As the Obama administration prepared to send the new U.S.-Russian arms treaty to the Senate for ratification, differences emerged Monday between Moscow and Washington over whether the agreement limits missile defenses.
Speaking to reporters in Moscow, Russian Foreign Minister Sergey Lavrov said Russia reserved the right to pull out of the Strategic Arms Reduction Treaty, or START, if the level of U.S. missile defense forces increases.
"The package of documents presumes that the treaty is concluded in circumstances where the parties have appropriate levels of strategic defensive systems," Mr. Lavrov said. "Changing these levels gives each party the right to decide the question of its future participation in the process of reducing strategic offensive arms."
However, Ellen Tauscher, undersecretary of state for international security and arms control, told reporters on Monday that the new START would not limit or bind U.S. actions whatsoever with regard to missile defense.
"As we've talked before, the presidents met in July, and they made it very clear that there is an interrelationship between strategic offensive and strategic defensive weapons," she said. "But there is no limit or constraint on what the United States can do with its missile defense system."
The difference in interpretation on missile defense could determine the fate of START when the administration sends the document to the Senate for ratification. President Obama will need the support of at least eight Republicans to reach the 66-vote margin for a two-thirds majority required under the Constitution for treaty ratification.
Ms. Tauscher said the administration's goal is to send the treaty to the Senate by late spring, with the goal of ratification by the end of the year.
John R. Bolton, former arms-control director at the State Department and ambassador to the United Nations under President George W. Bush, said he will withhold judgment on the treaty until the administration responds to congressional queries under oath about it. Mr. Bolton is an influential voice among Republicans on arms-control issues.
"It is still not clear what the expectation is on missile defense or on subsequent negotiations on missile defense," Mr. Bolton said. "Is there a commitment for further discussions on missile defense? I don't think we will know this until we see the terms of the treaty itself and there is a chance for questions in congressional testimony."
The text of the treaty, which will replace the 1991 START, which expired in December, has not been made public. The treaty is expected to be signed in Prague next month.
The ranking member of the Senate Foreign Relations Committee, Richard G. Lugar, Indiana Republican, has said he will vote for START. But other influential senators, such as Sen. Jon Kyl, Arizona Republican, have not indicated where they stand on the pact.
A group of 41 senators wrote to Mr. Obama in December to remind him that last year's National Defense Authorization Act contains language that links any new strategic arms treaty to a much-needed program to modernize aging U.S. nuclear forces.
The senators, representing enough votes to block ratification, stated in the letter that the nuclear modernization plan should be fully funded and sent to the Senate along with START for ratification.
Last year, the Obama administration announced that the United States would remove missile-defense installations in the Czech Republic and Poland, in part to resolve what the administration viewed as an unnecessary irritant in U.S.-Russian relations. Moscow opposed the stationing of ground interceptors in Poland and radar in the Czech Republic.
Mr. Obama has said that he instead will deploy a system called a "phased adaptive approach" involving sea-based and less capable missile defenses oriented to hitting medium-range missiles from Iran rather than longer-range missiles capable of reaching the continental United States.
Ms. Tauscher said START represented the end of a new engagement process with Russia.
"I think that this process, this journey over the last year — President Obama and President [Dmitry] Medvedev, and Mr. Lavrov and Secretary [of State Hillary Rodham] Clinton setting the reset button — this has been a transformational exercise," she said.
The undersecretary said the START process "is also the first exercise where we have worked cooperatively with the Russians on something of mutual benefit, where we have improved the relationship. In and of itself, the negotiation has improved the relationship."
Steven Pifer, a senior fellow at the Brookings Institution and a former U.S. arms-control specialist, said the preamble to START will "acknowledge an interrelationship between offense and defense. But I also understand there are no limits on current or planned missile defense in the treaty itself."
Mr. Pifer said he anticipates a "unilateral statement from the Russians" that would state more clearly the Russian understanding that changes in missile defense could prompt withdrawal. But Mr. Pifer said such a statement should not concern U.S. diplomats or senators.
"Who cares?" he said. "There is a supreme interest withdrawal clause that goes back to the original START treaty and can be invoked for any reason by either side so long as they provide six months' notice."
The bulk of START would limit the U.S. and Russian nuclear arsenals. The 1991 treaty reduced offensive weapons at the end of the Cold War to 6,000 warheads for each side. A subsequent 2002 agreement reduced arsenals to 2,200 warheads for each side. That agreement, however, had no verification component or counting rules. The new START would further limit offensive warheads to 1,550 for each side and is said to contain specific verification provisions.
Russia is thought to have no more than 2,600 active warheads, and the United States has 2,200 active warheads. The Union of Concerned Scientists, which counts each deployed missile as one warhead and each deployed bomber as one warhead, says the United States has 1,762 warheads and Russia has 1,741.
Mr. Bolton said the limits for the United States are too low.
"As I understand it, it is 1,550 for both parties. It is a mistake to have a limit equal to the Russians, given our global nuclear umbrella commitment," Mr. Bolton said.
He pointed out that the U.S. umbrella extends to Australia, Japan and South Korea, as well as the countries in NATO.