Owens said even worse was the hypocrisy of Republicans attacking wage laws and project labor agreements, even though many House Republicans are on record supporting them.

There is substantial division within the union community over whether to support the pipeline project. There is also major disagreement about how many jobs the project will create. Supporters have claimed it could be as many as 130,000, but estimates from the pipeline company and the State Department predict a fraction of that.

In November, Obama postponed a decision on the pipeline until after the 2012 elections. But Republicans in Congress are hoping to force his hand by working to tie approval of the pipeline to an extension of the payroll tax cut.

— This post was updated at 1:13 p.m.