The US Senate voted down Thursday a measure to start building the controversial Keystone XL oil pipeline between Canada and the Gulf Coast of Texas despite President Barack Obama's opposition.

The Senate measure was introduced by minority Republican lawmakers upset at Obama's decision to delay a decision on the $7 billion pipeline until 2013.

The amendment, attached to a broader transportation bill, would have bypassed the administration to begin pipeline construction. Obama, however, would still have to sign the measure into law and could have vetoed it.

With the Senate vote, opposition Republicans can claim that Obama's fellow Democrats have turned down a project supporters insist would quickly create 20,000 US jobs and help bring down fuel prices in the sour economy.

The amendment was rejected 56-42. Sixty votes were needed for the measure to be approved.

"President Obama had the opportunity to create thousands of new jobs right away, plus bolster job prospects for thousands more throughout the manufacturing supply chain," said Republican Senator Richard Lugar, who co-authored the measure.

"Allowing seven billion dollars of private economic activity should be a no-brainer."

He claimed that Obama "caved to pressure from extreme environmentalists by rejecting Keystone XL jobs and security."

The pipeline has turned into a major issue in US politics, with environmentalists waging months of protests and the oil industry funding an advertising blitz.

Environmentalists fear an accident along the 1,700-mile (2,700-kilometer) pipeline would spell disaster for aquifers in central US Great Plains states. They also oppose the project because exploiting the oil sands requires energy that generate a large volume of greenhouse gases.

Under the amendment, there was "no protection for workers, no protection on the environment, and I believe higher prices for American businesses and American consumers," said Democratic Senator Ron Wyden.

Obama's personal phone calls to wavering senators "may have tipped the balance against this legislation," complained Republican Senate Minority Leader Mitch McConnell.

"When it comes to delays over Keystone, anyone looking for a culprit should now look no further than the Oval Office."