Republican White House hopefuls on Friday slammed the Obama administration's rejection of the Keystone XL oil pipeline project, saying the decision would hurt the U.S. economy.

"The Obama admin's politically motivated rejection of the Keystone XL pipeline is a self-inflicted attack on the U.S. economy and jobs," former Florida Governor Jeb Bush said on Twitter.

President Barack Obama's rejection of the proposed oil pipeline from Canada was a victory for environmentalists, who have lobbied against it for years. Supporters countered that the pipeline would boost America's energy security and create construction jobs.

Obama told a news conference on Friday he had concluded the pipeline, proposed by TransCanada Corp, would not help the U.S. economy over the long term.

Republicans seeking the White House in the November 2016 presidential election quickly voiced their disagreement.

Presidential candidate and U.S. Senator Marco Rubio vowed to approve the pipeline if he wins the White House. "President Obama's backward energy policies will come to an end," he said in a statement.

Louisiana Governor Bobby Jindal, also a White House hopeful, accused Obama of giving in to "radical environmentalists."

Obama did get support from Democratic presidential candidates on Friday.

"It is insane for anyone to be supporting the excavation and transportation of some of the dirtiest fuel on earth," U.S. Senator Bernie Sanders of Vermont said in a statement.