U.S. military leaders dismissed Republican claims that a new arms treaty with Russia would hamper America's missile defense efforts as supporters tried Thursday to nudge the pact toward ratification in the Senate.

President Barack Obama has pushed for approval of the treaty in Congress' lame-duck session, a chance for a foreign policy victory to cap a politically difficult year. Conservative Republicans stand in the way, asserting that the United States made too many concessions in negotiations with Russia and the treaty would limit U.S. defense options.

"They get everything out of it," insisted Sen. Jon Kyl, R-Ariz. "I don't know what we get out of it except for the president to say he made another arms control deal with Russia."

Countering those arguments — though unlikely to appease some Republicans — Defense Secretary Robert Gates told reporters at the White House on Thursday that the treaty "in no way limits anything we want or have in mind on missile defense."

Marine Gen. James Cartwright, vice chairman of the Joint Chiefs of Staff, echoed Gates' assertion, saying the New START treaty has "no prohibitions" to America's ability to move forward on missile defense.

"We need START and we need it badly," Cartwright said.

"START" stands for Strategic Arms Reduction Treaty.

The treaty, signed by Obama and Russian President Dmitry Medvedev in April, would limit each country's strategic nuclear warheads to 1,550, down from the current ceiling of 2,200, and establish a system for monitoring and verification. U.S. weapons inspections ended a year ago with the expiration of the 1991 arms control treaty.

Supporters are pushing for ratification in the closing days of the year because prospects for passage will dim when Republicans increase their numbers by five senators in January. The Constitution requires approval by two-thirds of the Senate to ratify a treaty.

Backers of the pact and the Obama administration were encouraged by a 66-32 vote on Wednesday to move ahead on debate, boosting Senate Democratic leader Harry Reid's contention that he has the votes for ratification.

In an all-out effort, the administration sent its chief negotiator on the treaty and other officials to Capitol Hill to respond rapidly to criticism and attempt to win over more Republicans. All 58 Democrats and independents were expected to support the New START deal, but it needs Republican votes to pass.

"We don't do these treaties as a favor to the Russians," negotiator Rose Gottemoeller told reporters at a briefing. "They are in our national security interests."

Proponents of the treaty cite the renewed weapons inspections and say the pact would keep the two biggest nuclear powers on the path to reducing their arsenals. Opponents assert it would restrict missile defense and argue that it has insufficient procedures to verify Russia's adherence.

Missile defense is a cornerstone national security program for Republicans, begun 25 years ago by President Ronald Reagan. It would create a system aimed at protecting the United States and its allies from ballistic missile attacks.

Some Republicans contend that the preamble to the treaty and its language on the relationship between strategic offensive and defensive weapons could complicate U.S. efforts to expand its missile defense.

"START straitjackets the United States missile defense capabilities," Sen. John Barrasso, R-Wyo., said on the Senate floor.

Several Republicans said they were determined to amend the treaty, which would effectively kill it because any changes would require new negotiations with Russia. None of the amendments was offered, however, during the daylong debate Thursday.

Administration officials stress that the preamble is not legally binding, that the language is similar to previous treaties and that the accompanying resolution of ratification from the Senate Foreign Relations Committee said the treaty would not constrain missile defense.

Not all Republicans share the concern about missile defense.

Sen. Richard Lugar of Indiana, the top GOP lawmaker on the Foreign Relations Committee, said in a letter to colleagues that under the treaty, "we will continue to control our own missile defense destiny, not Russia."

Evoking Reagan, Democratic Sen. Ben Nelson of Nebraska said the former president "laid the foundation for today's START treaty."


Associated Press writers Julie Pace and Desmond Butler contributed to this report.