The U.S. Senate has voted to close out debate on a new arms control treaty with Russia, setting the stage for ratification of the accord.
The vote was 67-28 and was seen in part as a proxy vote for the final tally. President Barack Obama considers the treaty his top foreign policy priority in the postelection Congress.
Almost a dozen Republicans joined all the Democrats in calling for an end to the debate. Vice President Joe Biden and Secretary of State Hillary Rodham Clinton were at the Capitol lobbying lawmakers.
Earlier in the day, Obama locked up the votes for ratification of the treaty as at least 10 Republicans said they would back the accord. A final vote is likely on Wednesday.
"After much study and discussion, I have decided to support ratification of the New START treaty, viewing it as a modest step forward in our efforts to reduce the risk of nuclear war," Lisa Murkowski said in announcing her support Tuesday. "For the United States, it maintains our strategic or long range nuclear weapons capability, while also allowing the U.S. to return to on-the-ground verification of Russia's nuclear stockpile."
Defense Secretary Robert Gates, in a statement Tuesday, urged the Senate to ratify the pact this week. He said the treaty would "provide the necessary flexibility to structure our strategic nuclear forces to best meet national security interests."
The administration has stepped up its lobbying of pivotal Republicans to win approval of the treaty, which has become Obama's main priority for the remaining legislative session.
Republicans and Democrats were discussing amendments to the accompanying resolution, not the treaty, that would deal with Republican problems with missile defense and build support for the agreement.
The United States and Russia negotiated the New START pact to cap nuclear weapons and restart weapons inspections in the spirit of U.S. efforts to reset the relationship between the former Cold War foes.
The pact with Russia would set a limit on both countries' nuclear warhead stockpile at 1,550, down from 2,200, and set up a system to monitor and verify those reductions, reports CBS News congressional correspondent Nancy Cordes. U.S. weapons inspections ended a year ago with the expiration of a 1991 treaty.
Treaty backers were heartened as several Republicans broke ranks, voting against three Republican amendments that would have effectively killed the treaty.
Obama, who delayed his holiday vacation, lobbied senators by phone as he pressed to complete the treaty before January. Vice President Joe Biden also called lawmakers.
Bolstering Obama's argument for quick action, Adm. Mike Mullen, chairman of the Joint Chiefs of Staff, sent a letter to lawmakers reiterating support for the accord.
"This treaty enhances our ability to do that which we in the military have been charged to do: protect and defend the citizens of the United States. I am confident in its success as I am in its safeguards. The sooner it is ratified, the better," Mullen wrote.
Senate Foreign Relations Committee Chairman John Kerry, a Democrat, read parts of Mullen's letter at a closed briefing.
Despite the letter, several conservative Republicans insist the treaty would restrict U.S. options on a missile defense system to protect America and its allies and argue that the accord has insufficient procedures to verify Russia's adherence.
On CBS' "Face the Nation" Sunday, Sen. Lindsey Graham, R-S.C., said.
"We haven't had a serious debate on START," said Graham. "We've been fighting a multiple-front war to try to do every special interest group's bidding in the lame-duck session."
"If you want to have a chance of passing START, you better start over and do it in the next Congress, because this lame duck has been poisoned," Graham told CBS News chief Washington correspondent Bob Schieffer.
Politics coursed through the debate Monday as Republicans were still peeved by Senate Majority Leader Harry Reid's decision to interrupt the six days of treaty consideration for votes onserving openly in the military and an unsuccessful immigration measure, legislation they considered sops to the Democratic Party's liberal base.
"No senator should be forced to make decisions like this so we can tick off another item on someone's political check list before the end of the year," Minority Leader Mitch McConnell, R-Ky., said.
Obama suffered a self-described "shellacking" in the Nov. 2 midterm elections as his party lost control of the House and suffered an erosion in its Senate majority. Yet he has scored two major political wins in Congress' postelection session - overwhelming bipartisan passage of the tax deal he cut with Republicans and repeal of the ban on gays serving openly.