In a room full of Democratic and Republican present and past national security officials -- including President Obama's Secretary of State Hillary Clinton and former Secretary of State Henry Kissinger -- President Obama called on the Senate today to quickly pass the U.S.-Russia nuclear arms treaty.
"It is a national security imperative that the United States ratify the new START treaty this year," Obama said.
The agreement would reduce the U.S. and Russian arsenals of strategic warheads to 1,550 each and restart inspections that stopped when a previous treaty expired nearly a year ago.
As of now, the president can count on 60 Senate votes -- 59 Democrats plus Indiana Sen. Richard Lugar, the top Republican on the Foreign Relations Committee. Sixty-seven votes are needed for treaty ratification, with Sen. Jon Kyl, R-Ariz., all but threatening to block the treaty from coming to the floor for a vote.
"As Ronald Reagan said, we have to trust, but we also have to verify," President Obama said today, arguing that the treaty is needed to keep an eye on Russia's nuclear arsenal. "In order for us to verify, we've got to have a treaty."
"If we don't, then we don't have a verification regime," he said. "No inspectors, no insights into Russia's strategic arsenal, no framework for cooperation between the world's two nuclear superpowers."
Kyl was joined today by Rep. Roy Blunt, R.-Mo. and nine other incoming GOP senators in pushing for a delay, however, saying that treaty ratification should not be rushed during a lame-duck session. And other Republicans say they have concerns that some language in the treaty ties the hands of the U.S. when it comes to plans for missile defense. Defense Secretary Robert Gates and other Republicans say that concern is not based on facts.
"If it was so important, it should have gotten done. They should have gotten it done," Blunt told ABC News today. "Nothing like this has ever been done in a lame-duck session before."
Republican lawmakers also have been pushing for money to modernize the nuclear arsenal. The White House recently signaled it would be willing to add more than $4 billion over 10 years to that end.
The showdown comes as a separate confrontation brews over the president's push for accused terrorists at Guantanamo Bay to be tried in civilian courts instead of military tribunals.
On Wednesday, a jury in New York convicted Ahmed Ghailani of one of 285 charges related to al Qaeda's 1998 U.S. Embassy bombings in Africa. The bombings killed 224 people. Ghailani was convicted of conspiring to destroy government buildings, a charge that brings a minimum of 20 years in prison.
Obama's critics have assailed the presidential push to try detainees in civilian courts instead of military commissions.
"The administration's approach to prosecuting terrorists has been deeply misguided and indeed potentially harmful as a matter of national security," said Sen. Mitch McConnell, R-Ky, the Republican leader.
"He could have well been acquitted on all counts -- that is pretty much obvious," Sen. Jeff Sessions, R-Ala., the ranking Republican on the Senate Judiciary Committee, told ABC News. "To try a military combatant, any soldier combatant who is at war with the United States, in the civilian courts is not correct. It is not the right policy."
But supporters of the civilian trials note that the case against Ghailani was compromised because the defendant was interrogated by CIA officers using methods commonly considered torture -- "enhanced interrogation techniques" sanctioned by the Bush administration.
"Despite the fact that torture went on, this skillful prosecution still was able to get a jury to come to guilty. That's the important thing," said Rep. Anthony Wiener, D-NY. "This was a very difficult case, it was skillfully prosecuted and at the end of the day, the guy who did these dastardly crimes will be rotting in jail...that's what we should keep focused on."
ABC News' Matt Jaffe and the Associated Press contributed to this article.