The US Senate voted Wednesday to formally open debate on a landmark nuclear arms control treaty with Russia, as the White House blasted Republican efforts to derail the accord as a dangerous "new low."

Lawmakers voted 66-32, almost exactly down party lines, to take up the new Strategic Arms Reduction Treaty (START), which President Barack Obama has made a lynchpin of his effort to "reset" relations with Russia.

The figure showed Democrats within striking distance of attracting the nine Republicans necessary to reach the 67 votes needed to ratify the treaty, which Obama and Russian President Dmitry Medvedev signed in April.

The agreement -- which has the support of virtually every present and former US foreign policy or national security heavyweight -- restricts each nation to a maximum of 1,550 deployed warheads, a cut of about 30 percent from a limit set in 2002, and 800 launchers and bombers.

The agreement, which has broad American public support, would also return US inspectors who have been unable to monitor Russia's arsenal since the agreement's predecessor lapsed in December 2009.