Most Americans favor building the Keystone XL oil sands pipeline, according to a CNN-ORC poll released Thursday.

Fifty-seven percent of the 1,011 adult American respondents said they want the Canada-to-Texas project to get built, compared with 28 percent who oppose the 1,700-mile pipeline.

Four in five Republicans favored building Keystone XL, compared with about two in five Democrats. Age was also factor, as Americans who were at least 65 years old were most likely to support the pipeline (62 percent) while those between ages 18 and 34 were least likely to do so (47 percent).

The $8 billion pipeline has been under federal review for more than six years as its builder, TransCanada Corp., needs a cross-border permit to complete the northern leg.

Republicans and centrist Democrats have criticized President Obama for the time it has taken to review the project, and are trying to pass legislation to approve Keystone XL. The House passed its bill last week, and the Senate will begin considering amendments to the bill next week.

But Obama has threatened to veto the measure, saying he wants to complete the federal review before making a decision on the pipeline. It's not clear whether either chamber will be able to override a veto.

The poll was conducted via landline and cell phone between Dec. 18 and 21. It contains a 3 percent margin of error.