WASHINGTON — Congress is getting a controversial U.S.-Colombia free-trade agreement from President Bush and must vote on it within 90 legislative days.

Many Democrats and union groups denounced Bush's decision on Monday, raising the prospect that the deal will be defeated.

Democrats contend that Colombia has not done enough to halt violence, protect labor activists and demobilize paramilitary organizations. The president disagreed, saying Colombia has addressed the issues.

"If Congress fails to approve this agreement, it would not only abandon a brave ally; it would send a signal throughout the region that America cannot be counted on to support its friends," Bush said in a ceremony with members of his Cabinet where he signed the letter transmitting the agreement to Congress.

Bush's action will force Congress to take up the proposal under a fast-track process that will require votes within 90 legislative days, which counts the days that Congress is in session. Officials said Bush is acting now in order to force a vote before Congress leaves in the fall for the campaign season.

Democrats and labor unions blasted the move, the first time a president has used his fast-track authority to force a congressional vote over the objections of the party controlling Congress.

"The president's decision to act unilaterally in sending the free-trade agreement disregards three decades of established precedent under fast-track legislation and demonstrates yet again his disrespect for Congress," said Senate Majority Leader Harry Reid.

House Speaker Nancy Pelosi and House Ways and Means Committee Chairman Charlie Rangel said they could not support the Colombia pact "under present circumstances."

"The president's apparent disregard for the economic insecurity faced by millions of struggling American families highlights a misplaced set of priorities," Rangel and Pelosi said in a joint statement.

Bruce Raynor, head of Unite Now, a 465,000-member union representing workers in the apparel and textile industries, said it was an outrage for Bush, during a time of economic crisis, to send Congress a trade agreement "with a country that has one of the most ruthless records of repression of the trade-union movement."

Business groups, including the National Association of Manufacturers and the U.S. Chamber of Commerce, applauded Bush's move and said they would work to get the Colombia deal through Congress.

The administration insisted the deal would be good for the United States economically because it would eliminate high barriers that U.S. exports to Colombia now face, while most Colombian products are already entering the United States duty-free under existing trade-preference laws.

Trade analysts said Bush's effort faced long odds, given how hard it is to get Congress to approve free-trade measures at any time, much less an election year when unemployment is rising and the nation could be slipping into a recession.

"This is a very high-stakes gamble for what is actually a fairly small agreement, but one with huge political overtones," said Gary Hufbauer, a trade expert with the Peterson Institute, a Washington think tank.

Bush has staked out free trade as one of his chief economic legacies, winning a bruising battle to implement the Central American Free Trade Agreement with six countries in Latin America, as well as a number of individual pacts. While two other agreements with Panama and South Korea are also pending, analysts said the Colombia agreement is likely to be the last one that has any chance of winning approval in Bush's last year in office.