By Patricia Zengerle and Richard Cowan

WASHINGTON (Reuters) -- A Republican-backed effort to kill the Iran nuclear agreement was blocked in the U.S. Senate on Thursday, handing a major foreign policy victory to President Barack Obama.

Forty-two Democrats and independents voted against a measure to advance the bill, meaning opponents of the nuclear agreement failed to get the 60 votes needed in the 100-member chamber to proceed with a resolution of disapproval of the pact.

Democrats said that the vote killed efforts in the Republican-controlled Congress to derail the nuclear pact, between six world powers and Tehran. Had opponents of the agreement passed such a resolution, Obama would have been barred from waiving many U.S. sanctions on Iran, a crucial part of the nuclear pact.

But the Senate's Republican majority leader, Mitch McConnell, immediately took steps to clear the way for another Senate vote on the matter.

“We'll revisit the issue next week and see if maybe any folks want to change their minds,” he said.

Under a law Obama signed in May, Congress has a 60-day period ending on Sept. 17 to pass a resolution disapproving of the international agreement.

Republican leaders of the House of Representatives were also pushing ahead with legislation critical of the nuclear agreement.

The House voted strictly along party lines to clear the way for debate on Thursday on three bills, none of which will have a direct impact on the nuclear pact.

One of the three measures is a resolution finding that Obama has not complied with theIran nuclear review act, the second is a motion of approval of the nuclear deal and the third would seek to suspend Obama's right to waive sanctions.

House Republicans came up with the plan for the three votes on Wednesday after a rebellion by some of the party's most conservative lawmakers delayed a vote on a resolution of disapproval of the nuclear agreement.

There are no plans now for the Senate to vote on legislation similar to the three measures being considered in the House.

(Additional reporting by Richard Cowan; Editing by Susan Heavey, Bill Trott and Steve Orlofsky)