(Reuters) - House Speaker John Boehner, signaling a lack of Republican support for a stalled $260 billion transportation bill, said Thursday he was ready to pursue a less ambitious version under consideration by the Democratic-controlled Senate.

A day after imploring House Republicans to end their deep divisions over the five-year measure to rebuild roads, bridges and railways, Boehner moved a step closer to giving up on the troubled House bill altogether.

The current plan is to see what the Senate can produce and to bring their bill up, Boehner told a news conference. In the meantime we're going to continue to have conversations with members about a longer-term approach, which most of our members want. But at this point in time, the plan is to bring up the Senate bill or something like it.

Being forced to take up the Senate bill would be another potential setback for Boehner, who has repeatedly struggled to whip up support among conservative Republicans on spending bills. He also has castigated the Senate for failing to consider jobs bills passed by the lower chamber.

The shift to a Senate bill also means Boehner would have to sell House Republicans on a two-year, $109 billion measure that will not contain several provisions they favor.

The Senate on Thursday rejected an amendment that would approve TransCanada Corp's Keystone XL pipeline project from Canada to Texas.

The House version has faced difficulties from the start, alienating fiscally conservative Republicans over its price tag while Democrats and some Republicans have opposed a provision that would end dedicated funding for mass transit projects.

But House Transportation and Infrastructure Committee Chairman John Mica said he was not giving up on the measure, and that his staff was working with the Boehner and other Republican leaders to try to marshal sufficient votes for passage.

Time is running short, however, as current funding for road and rail construction projects expires on March 31. As many as 1.8 million construction workers would face layoffs if a new measure is not signed into law by then, Democrats say.

We're not going to let March 31 go by and experience any kind of a shutdown. That is not an option under consideration, Mica said, adding that one possibility was a temporary extension.

(Additional reporting by Richard Cowan; editing by Vicki Allen and Mohammad Zargham)

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