WASHINGTON -- Senate Democrats appeared on the verge of dealing a stinging blow to President Barack Obama Tuesday, by stalling legislation that would grant him authority to fast-track international trade deals with little congressional interference. Democrats, including several who favor Obama's trade agenda, appeared united enough to defeat a procedural vote set for Tuesday afternoon that would have advanced legislation that grants the president so-called Trade Promotion Authority, which gives him the power to cut trade deals and expedite their passage through Congress without amendments or procedural hurdles, such as Tuesday's vote. The fast-track authority is seen as essential to passing the mammoth Trans-Pacific Partnership, a secretive trade deal with 11 other Asian-Pacific countries, and the equally large Transatlantic Trade and Investment Partnership with Europe.