Lawmakers on Thursday proposed empowering US trade negotiators to push ahead major deals with Pacific Rim and European Union nations, but the move faces stiff opposition. Three key lawmakers on trade policy introduced a bill to give President Barack Obama "fast-track authority," which would allow his team to negotiate agreements that Congress could approve or reject -- without making changes. Supporters said the four-year extension of the powers, which last ended in 2007, is indispensable to speeding up trade negotiations. The Obama administration has put a high priority on the 12-nation Trans-Pacific Partnership, seeing it as tying the United States more firmly to the dynamic Asia-Pacific region. The administration has also opened talks with the European Union on a potentially sweeping pact known as the Transatlantic Trade and Investment Partnership. The trade authority legislation "is critical to a successful trade agenda," Senator Max Baucus, a Democrat who heads the Senate Finance Committee, said in a statement. "It is critical to boosting US exports and creating jobs. And it's critical to fueling America's growing economy," said Baucus, who Obama recently nominated to be ambassador to China. The legislation outlines US objectives in trade deals, including the protection of intellectual property and assurances against currency manipulation. Some lawmakers accuse Japan, which is part of the Trans-Pacific Partnership, and especially China, which is suspicious of the trade pact, of artificially weakening their currencies to promote exports. "This legislation will be instrumental to ensuring that our country's current trade negotiations in Asia and Europe are a success and that these agreements meet the high standards necessary for congressional approval," said Senator Orrin Hatch, the top Republican on the Senate Finance Committee. The bill was also introduced in the House of Representatives by the head of the parallel committee, Ways and Means Committee Chairman Dave Camp, a Republican. But in November, 151 House Democrats -- three-quarters of the party's membership in the House -- signed a letter opposing fast-track authority. The Ways and Means Committee's top Democrat, Representative Sandy Levin, said that the proposal "has fallen far short" in addressing changes in the global economy. "We must do more to ensure that our trading partners do not gain competitive advantages through weak labor and environmental laws and enforcement -- a challenge that Vietnam's inclusion in TPP makes clear," Levin said in a statement referring to the Trans-Pacific Partnership. Levin also called for Congress to renew a program that expired last month that supports US workers hurt by trade. The assistance had previously been renewed after pressure from Levin and other labor-friendly Democrats in exchange for approving free trade agreements with South Korea, Colombia and Panama in 2011.