Liberal groups vow to block Obama's and GOP's bid to 'fast track' multinational trade deals

Trade pacts have a way of creating odd politics. That's why advocates hope new trade agreements might advance this year despite tensions between the Republican Congress and the Democratic White House on many other issues.

President Barack Obama wants Congress to restore presidential powers to negotiate multinational trade deals that Congress can accept or reject, but not amend.

This "trade promotion" or "fast track" authority is crucial to keep critics on the left and right from attaching killer amendments.

Many Republicans favor freer trade. But many liberal groups vehemently oppose it, saying that it encourages companies to ship U.S. jobs overseas.

Obama and his allies say they must do a better job of explaining free trade's benefits to American workers in the new global economy.