WASHINGTON (Reuters) - President Barack Obama said on Wednesday he would reject any congressional efforts to tie an extension of the payroll tax cut to support for the Keystone XL oil pipeline from Canada.

Speaking at a news conference with Canadian Prime Minister Stephen Harper, Obama said the U.S. government would hold a "rigorous" process to look at approving or rejecting the pipeline. A decision has been delayed until early 2013.

Harper said Obama indicated he would have an "open mind" about the final outcome. Obama said health, safety, and environmental questions about the project had to be answered.

(Reporting by Jeff Mason and Matt Spetalnick)