Senior U.S. lawmakers reached agreement on Thursday on a bill to give the White House "fast track" authority to negotiate a trade pact with 11 other Pacific nations that is central to President Barack Obama's strategic shift toward Asia.

The agreement sets the stage for a tough legislative battle over Obama's proposed Trans-Pacific Partnership, which would connect a dozen economies by cutting trade barriers and harmonizing standards in a deal covering two-fifths of the world economy and a third of global trade.

The bill gives lawmakers the right to set negotiating objectives but would restrict them to a yes-or-no vote on trade deals such as the ambitious TPP, a potential legacy-defining achievement for the Obama administration.