* Gibbs says Senate will take up treaty after tax vote
* Advocates say they have votes to ratify the accord
* "Issue of national security," retired general says
By David Alexander
WASHINGTON, Dec 13 (Reuters) - Administration officials and other proponents of the New START nuclear arms treaty with Russia expressed increasing confidence on Monday that they have the support needed to ratify the accord once the U.S. Senate brings it to a vote.
Debate on the treaty has not yet been scheduled, but White House spokesman Robert Gibbs told reporters he expected it to be "one of the next couple of pieces of business that the Senate will move to" after debate on tax legislation is concluded.
"Our belief is, as you've seen a number of Republican senators come out, that ... this is a treaty ... that has the votes to pass the Senate and I believe will pass the Senate before Congress goes home for the holidays," Gibbs told a White House briefing.
Senator Richard Lugar, the top Republican on the Senate Foreign Relations Committee, has said the treaty can get more than the 67 votes needed for ratification in the 100-member chamber, said Mark Helmke, his senior adviser.
Increased confidence in ratification of the treaty follows a series of announcements in recent days by Republicans who threw their support behind the accord, including former President George H.W. Bush.
Senators Olympia Snowe and Susan Collins endorsed the agreement on Friday. Senators Judd Gregg, George Voinovich and Lamar Alexander have said they were leaning toward supporting it.
U.S. President Barack Obama and Russian President Dmitry Medvedev signed the New Strategic Arms Reduction Treaty, or New START, in April. In addition to cutting deployed nuclear warheads, the agreement puts limits on the number of missiles and nuclear bombers on both sides.
Ratification of the accord was thrown into doubt last month when Senator Jon Kyl, the top Republican negotiating with the administration on the treaty resolution, said he did not think there was enough time to debate it before the end of the year.
Democrats fear the accord could be much more difficult to pass when the new Congress takes office in January. Democrats lost control of the House in the November elections and saw their majority in the Senate shrink.
Failure to pass the treaty in the current Congress would send it back to the Foreign Relations Committee for reconsideration, a process that could take weeks as the new lawmakers get up to speed on the issues.
The treaty has the support of the Defense Secretary Robert Gates, Admiral Mike Mullen, chairman of the Joint Chiefs of Staff, and the rest of the military establishment.
But some Republicans have expressed concern about the accord, demanding the Obama administration provide adequate funding to modernize U.S. nuclear forces and expressing concern the treaty might limit Washington's ability to build missile defense systems.
Obama has pledged some $85 billion for nuclear modernization. Experts say the funding is adequate to ensure the arsenal remains in a high state of repair while also enabling officials to build new facilities to construct more up-to-date systems that would be more secure and effective.
"It's an issue of national security," retired Brigadier General John Adams, a member of the Consensus for American Security, told a briefing on Monday. "They need to do their duty and put this to a vote. And I believe if it comes to a vote it's going to get ratified." (Editing by Todd Eastham)