Ten Democratic senators have voted with Republicans to allow the progress of a bill to extend the Keystone oil pipeline, placing more political pressure on the White House to reconsider its proposed veto of the legislation.

The procedural motion was passed by 63 votes to 32, comfortably clearing the three-fifths majority needed to avoid a filibuster and falling just short of the two-thirds majority that would be needed to overcome a presidential veto when it comes to a final vote.

But some of the Democrats, who were also joined by Maine independent Angus King, may switch votes in future to avoid embarrassing Barack Obama who has said he is opposed to Congress interfering in a long-running administration review of the pipeline extension.

Keystone has become a symbolic battlefield for the administration’s climate change policy, with critics insisting that it will encourage the exploitation of heavily-polluting Canadian tar sands and supporters claiming it will create thousands of jobs.

The bill will now see various amendments added over the coming weeks, a process which could ultimately decide on its level of support among Democrats.

It was approved by the House of Representatives last week by 266-152 votes, a margin also short of the two-thirds majority in both chambers needed to overcome White House opposition.

The Obama administration has stood by its decision to reject the bill, even though a Nebraska court decision in favour of the Keystone route removed one of its remaining objections.

The Democrats who joined senator King in voting for cloture on the motion to proceed included: Michael Bennet of Colorado, Tom Carper of Delaware, Bob Casey of Pennsylvania, Joe Donnelly of Indiana, Heidi Heitkamp of North Dakota, Joe Manchin of West Virginia, Claire McCaskill of Missouri, Jon Tester of Montana, Tom Udall of New Mexico and Mark Warner of Virginia. King has said he would vote against final passage, and five senators have not voted at all yet.