Secretary of State Hillary Rodham Clinton said Tuesday she is confident the administration will win enough Republican votes in the Senate to ratify a nuclear arms treaty with Russia.

Richard Lugar of Indiana is the only Senate Republican thus far to publicly express his support for the treaty, known as "New START," but Clinton said she has indications others will follow suit.

Speaking to reporters at the State Department, Clinton argued that U.S. national security is at risk if the Senate does not ratify the New START treaty signed in April by President Barack Obama and Russian President Dmitry Medvedev. She called it an urgent matter.

Faced with a relentless barrage of Republican criticisms of the treaty and their demands for more information, the Senate Foreign Relations Committee put off a vote until mid-September.

The committee must approve the treaty before the Senate could ratify it by the required two-thirds majority, 67 votes. That would require support from at least eight Republicans.

Clinton said that the decision last week by the committee chairman, Sen. John Kerry, D-Mass., to delay the vote was a gesture of good faith that underscores the push for bipartisan support.

"But when the Senate returns they must act, because our national security is at risk," Clinton said. "There is an urgency to ratify this treaty because we currently lack verification measures with Russia, which only hurts our national security interests. Our ability to know and understand changes in Russia's nuclear arsenal will erode without the treaty."

The treaty would reduce the limit on strategic warheads to 1,550 for each country, down about a third from the current ceiling of 2,200. It also would make changes in the old treaty's procedures that allow both countries to inspect each other's arsenals and verify compliance.

The chairman of the Senate Armed Services subcommittee on strategic forces, Ben Nelson, D-Neb., told a nuclear weapons symposium in Omaha on Tuesday that without the new treaty, U.S. insights into Russian nuclear forces would deteriorate, creating uncertainty.

"We'd have a tendency for U.S forces to overcompensate for what we don't know," Nelson said. "That's a losing strategy in an era of large budget deficits and needed fiscal constraint."