WASHINGTON -- Senate Democrats temporarily stalled progress Monday on a bill to approve the Keystone XL oil pipeline, the top priority of the Republican-controlled Congress.

In a 53-39 vote, the Senate blocked an attempt by Republican leaders to wind down debate. That's short of the 60 votes needed.

The vote caps a partisan dispute - which had the Senate working into the early hours last Friday - over the time granted to consider amendments on the bill.

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Majority Leader Mitch McConnell wants to move to pass the bipartisan legislation, which has 60 sponsors, including six Democrats. But Democrats argued they needed more time to offer and debate their additions.

"Senator McConnell promised Democrats an open amendment process and a full-throated debate on the Keystone pipeline, and we are holding him to that promise," Sen. Chuck Schumer, D-N.Y., said in a statement.

President Barack Obama has threatened to veto the bill if it reaches his desk.

Some Democrats who two months ago supported a bill approving the pipeline, including one of the bill's current sponsors, helped filibuster the move to limit debate.