The leaders spent more than an hour privately discussing trade issues as they opened a two-day meeting of the Group of Seven leading industrial nations. The talks in the majestic Bavarian Alps coincided with the delicate debate in Washington over giving Obama the authority to move trade agreements through Congress more quickly.

In addition to the summit events at Schloss Elmau, a one-time artist retreat turned luxury spa, Obama met privately with British Prime Minister David Cameron and joined German Chancellor Angela Merkel for beer and sausages in a nearby town.

Obama and his advisers voiced confidence in the trade push, but the effort faces a deeply uncertain future. The president's own Democratic Party is largely opposed to legislation that allows Congress to reject or approve, but not change, trade deals negotiated by the administration. In an unusual political role reversal, the president's reservoir of support has come from his Republican opponents.

If Obama succeeds, it would boost the prospects for Congress eventually ratifying the Trans-Pacific Partnership pact, a 12-nation consortium that includes G7 partners Japan and Canada. The other G7 nations -- Britain, France, Germany, and Italy -- have a stake in a U.S.-European Union trade deal that is on a slower course.

Richard Fontaine, president of the Center for New American Security, said that a failure to grant Obama the negotiating authority could affect his trade agenda. Fontaine said other nations probably would view U.S. lawmakers' decisions as "a proxy for American engagement in the world."

While the Senate already has sided with Obama, the House is another matter. Just 18 Democrats have expressed support publicly, and that is short of what the White House is believed to need in order to supplement affirmative GOP votes.

Four of those lawmakers travelled with Obama to Germany: Reps. Gerry Connolly of Virginia, Jim Himes of Connecticut, Eddie Bernice Johnson of Texas and Mike Quigley of Illinois. Their invitation appeared aimed both at rewarding lawmakers backing one of Obama's priorities and showing G-7 leaders that he is getting some Democrats to join the effort.

Democrats are under intense pressure from labour unions, liberal organizations and others opposed to the Asia-Pacific pact because they believe it would hurt U.S. workers and weaken environmental standards. Anti-free trade demonstrators were among the groups protesting near the summit site.

Obama has insisted the deal is "the most progressive trade deal in history" and would be a boon for the American middle class. White House spokesman Josh Earnest acknowledged that the G7 leaders have been carefully watching the debate unfold in the U.S. He said Obama's message to them is that lower trade barriers will benefit citizens in all countries that are party to the trade agreements.

With the end of his presidency closing in, Obama has made finishing the Asia-Pacific pact a central part of his legacy. And analysts warn that a failure to follow through on that goal would have damaging effects.

"That's going to be a major setback for the president and his agency, his legacy," said Matthew Goodman, a former Obama administration official and current scholar at the Washington-based Center for Strategic and International Studies. "I think it would be catastrophic for the U.S. position in Asia, in particular."

Negotiations over the Asia-Pacific pact are nearing a conclusion, but the U.S.-European Union talks have proceeded more slowly and could well slip beyond Obama's presidency. The presidential trade authority, if approved, probably still would apply, given that it would have a six-year lifespan.

British officials said Cameron was pushing G7 leaders to reach a deal by year's end. Merkel, in an interview with German television, said she wanted to work on the agreement "at top speed." In another interview, she said she and Obama discussed trade in their private session "because the American president also knows that there are certainly reservations in Germany."

Among opponents of Obama's push for the negotiating power, a chief concern about the European trade pact is that it could water down financial regulations. Sen. Elizabeth Warren, D-Mass., has argued that if the U.S. and European Union harmonize their financial regulations, it could lead to a race to the bottom and undermine a 2010 U.S. law that tightened restrictions on big banks.

Warren and others warn that given Republican opposition to that law, a future GOP president could use the trade deal to purposefully weaken the restrictions.

Associated Press writers Jill Lawless in London, David McHugh in Elmau, Germany, and Jim Kuhnhenn in Washington contributed to this report.