Gen. Brent Scowcroft (ret.), who served as National Security Advisor to two Republican presidents, told ABC News' Jake Tapper yesterday that he has been "frustrated" in his efforts to convince fellow Republicans to vote for the treaty.
"It's baffling me," he said.
"It doesn't tie our hands on missile defense," Scowcroft said, "as the president has already demonstrated; we're moving ahead on missile defense on Europe."
"There are things in the treaty people don't like," he continued, "but right now we have no oversight over what Russians are doing inside with their own nuclear systems" because the previous START treaty expired one year ago this month. "This would restore that, so we can carry forward all the accounting, the rules, the assurances, the inspections -- all the things giving us the confidence to go ahead. Without those it seems to me we're absolutely nowhere."
Other Republican foreign policy heavyweights including former secretaries of state Condoleezza Rice, George Schultz, Henry Kissinger, and former President George H.W. Bush had also expressed their support for New START.
The administration believed it would get the necessary support to approve the pact, but it wasn't taking any chances. Secretary of State Hillary Clinton remained in Washington to push for ratification before leaving town for vacation. In recent weeks, Clinton called nearly two dozen senators urging them to vote yes.
Today, Defense Secretary Robert Gates issued a statement pushing for ratification.
"This treaty stands on its merits, and its prompt ratification will strengthen U.S. national security," he said.
Yesterday, Sen. Kerry released a letter from the Chairman of the Joint Chiefs of Staff, Adm. Mike Mullen, supporting treaty ratification.
"This treaty has the full support of your uniformed military, and we all support ratification," Mullen wrote.
Support for the treaty emerged today from some Republicans, notably the third ranking Republican Sen. Lamar Alexander of Tennessee, Sen. Johnny Isakson of Georgia, and Sen. Bob Bennett of Utah. Those yes votes gave Democrats reason for optimism despite vows over the weekend from the top two Republicans, minority leader Mitch McConnell of Kentucky and whip Jon Kyl of Arizona to oppose the treaty.
ABC News' Jake Tapper, Jonathan Karl, Matthew Jaffe, and Luis Martinez contributed to this report.