By CARL HULSE

WASHINGTON — House Democrats exhibited unity on Thursday in voting to stall a trade pact with Colombia pushed by President Bush, but that vote masked deep party divisions on trade, an issue certain to become even more highly charged given consequential trade deals with South Korea and other countries in the pipeline.

An influential bloc of Democrats continues to favor expanded trading relationships with nations willing to meet labor and environmental conditions, putting them at odds with fellow Democrats allied with unions who blame free trade for the loss of thousands of American jobs since the 1970s. The fight has flared in the presidential campaign as well.

“There has been a split within the party, I think, that has become pretty evident,” said Representative Joseph Crowley of New York, who has backed previous trade deals. He attributes deepening Democratic resistance to trade agreements to what he calls the “Dobbsian effect” named for the CNN broadcaster and trade critic Lou Dobbs.

But Mr. Crowley and others inclined to entertain free trade agreements sided with Speaker Nancy Pelosi in voting 224 to 195 to put off consideration of the agreement with Colombia until the speaker decides the time is right — a move that infuriated the administration and House Republican leaders. All but 10 Democrats backed Ms. Pelosi while 6 Republicans joined in stalling the agreement.

Democrats said Mr. Bush tried to ram the trade agreement through despite warnings from lawmakers that the deal was in trouble, given the deteriorating domestic economic climate, the approaching election and concern about treatment of workers by the Colombian government. They said Congress had to make sure that Americans see lawmakers working on their behalf before opening the door to more trade with Colombia.

“If we are going to be successful in passing a trade agreement, we have to first tell the American people that we have a positive economic agenda,” Ms. Pelosi said.

But Republicans said Democrats were only hurting American workers since the agreement would level the playing field by eliminating duties on domestic goods entering Colombia, which already has significant duty-free access to the United States.

“Even postponing Congressional consideration of this agreement does tremendous damage to America’s competitiveness,” said Representative James McCrery of Louisiana, senior Republican on the Ways and Means Committee. “Colombia will buy tractors, mining equipment and fertilizer from Canada, France and Germany instead of Illinois, Georgia and Texas.”

President Bush and others noted that the decision could undermine Colombian President Álvaro Uribe, an ally who has been taking a harder line on narcotics traffickers and challenging the Venezuelan president, Hugo Chávez, a foe of the United States who has been trying to expand his reach in Latin America. House Republicans referred sarcastically to the Democratic plan to remove a 90-day deadline for considering the agreement as the “Hugo Chávez rule.”

“Today’s unprecedented and unfortunate action by the House of Representatives led by Speaker Pelosi to change the rules governing legislation to implement our trade agreement with Colombia is damaging to our economy, our national security and our relations with an important ally,” Mr. Bush said in a statement after the vote. “It also undermines the trust required for any administration to negotiate trade agreements in the future.”

Republicans said the reverberations for other emerging agreements are at least as significant as the impact on Colombia relations. Administration officials fear the House action on Colombia could significantly diminish the chances of a worldwide trade agreement still being negotiated and also pending deals with Panama and South Korea. President Lee Myung-bak of South Korea is scheduled to meet with Mr. Bush next week.