Ratification of a major nuclear arms control agreement with Russia by the United States Senate could become an issue in that country's congressional elections in November.

Republicans who oppose New START, a replacement for a Cold War-era treaty, are unlikely to kill the agreement. But they could force Democrats to delay a ratification vote until after the election, a scenario that could be damaging to U.S. President Barack Obama.

U.S. President Barack Obama and Russian President Dmitry Medvedev sign the New Strategic Arms Reduction Treaty in April in Prague. (Jason Reed/Reuters)

"A delayed ratification with a close vote would be a blow to U.S. leadership around the world," said Joseph Cirincione, president of the Ploughshares Fund, a foundation that advocates a world free of nuclear weapons.

"People would doubt the president's ability to negotiate other agreements."

The administration still hopes to win approval for New START before the Senate begins its summer break in August. Doing so would require the support of at least eight Republicans, along with all 57 Democratic and two independent senators to achieve the necessary two-thirds majority in the 100-member Senate.

Administration confident

The administration is expressing confidence, but so far only one Republican senator, Richard Lugar of Indiana, has announced his support.

Administration officials say they could wait until the "lame duck" session that takes place after November's election, but before new lawmakers are sworn in.

The White House does not want to postpone a vote until next year because Republicans are expected to pick up seats in the election.

Obama and Russian President Dmitry Medvedev signed the New START agreement in April. It would shrink 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 Heritage Action for America, a conservative advocacy group, has started a petition drive and may run political advertisements on the issue during the election season. It also is lobbying in the Senate.