President Bush signed legislation Tuesday giving U.S. presidents broad authority to negotiate global trade accords, and pledged to use his new powers to boost America's sagging economy.

"Trade expands choices for American consumers and raises living standards for our families," Bush said before signing a bill that restores the trade negotiating, or "fast track", authority that Congress has withheld from the White House since the Clinton administration.

"And now, after eight years, America is back in the business of promoting open trade to build our prosperity and to spur our economic growth," the president said.

Bush signed the bill after a quick trip to Bethesda, Md., for his annual physical. Flashing a thumbs up, Bush said he was "feeling good" after the checkup.

Minutes after the East Room ceremony, Bush boarded Marine One with his two dogs for a trip to Texas. With a quick wave, he was off to his Crawford ranch until Labor Day. His plans include meetings and fund-raising trips during his stay at his 1,600-acre Prairie Chapel Ranch and a visit there by Mexican President Vicente Fox on Aug. 26.

Criticized by Democrats for the long respite, Bush refuses to call it a vacation. "Remember. I'm just changing my office," he told an audience member who wished him a happy vacation.

Trade promotion authority allows the president to negotiate trade agreements that Congress may approve or reject but cannot change.

First given to the president in 1974, Congress refused to extend it after it expired during the Clinton administration in 1994, mainly because of concerns from Democrats and their allies that labor and environmental standards were being undermined.

"Five presidents before me had this advantage," Bush said. "But since the authority lapsed in 1994, other nations and regions have pursued trade agreements while America's trade policy was stuck in park."

The measure, sought by Bush since his first days in office, met strong opposition, largely from Democrats who balked at ceding to the president the powers over foreign commerce that the Constitution gives Congress. They warned against trade agreements that would encourage job-killing imports or undermine worldwide labor or environmental standards.

Bush dismissed the criticism.

"Trade is good for the American people and I'm going to use the trade promotion authority to bring these benefits to the American people," he said.

The bill includes a 10-year, $12 billion plan to help workers who lose their jobs because of trade and renews a program of low tariffs with Colombia and three other Andean nations designed to help their economies and make them less reliant on illegal drugs.

Bush said he will use his trade powers to help spur economic reforms across the globe.

"America's committed to building a world that trades in freedom and grows in prosperity and liberty," the president said. "Today, we have the tools to pursue that vision."

Backers of the bill said America in recent years has been left behind, participating in only three free trade agreements -- with Israel, with Jordan and in the North American Free Trade Agreement with Mexico and Canada. There have been 193 such agreements around the world since fast-track trade authority was taken away from the president.