In a rare example of the mountain coming to Mohammed, President Bush dropped by Capitol Hill Wednesday morning ahead of a vote on his priority foreign trade effort, the Dominican Republic-Central American Free Trade Agreement (search), commonly known as CAFTA.

A vote in the House could come as early as Wednesday, and Bush wanted to shore up support in the face of expected massive Democratic opposition.

Accompanied by Vice President Dick Cheney and U.S. Trade Representative Rob Portman (search), Bush attended the one-hour long, closed-door Republican caucus meeting to push for the deal's passage. The fact that Bush courted lawmakers on their own turf demonstrates how important passage is to the president.

According to House Majority Leader Tom DeLay (search), R-Texas, Bush urged Republicans to close ranks, telling them that while parochial interests concern some representatives, "we are here not only to represent our districts, but to represent the nation."

DeLay predicted a tough vote, but promised that "we will pass CAFTA tonight."

Many Republicans have wavered in their support of the agreement, which was signed by the Bush administration and the governments of Costa Rica, El Salvador, Guatemala, Honduras, Nicaragua and the Dominican Republic last year.

Last month, the Senate approved the measure, but some GOP House members are not happy with the deal, which would eliminate most tariffs and other trade barriers imposed by the six Latin American nations on U.S.-made goods, and also increase protections for investment and intellectual property.

Bush has said he believes the agreement will level the playing field when it comes to commodities such as sugar and textiles. House Republican leaders agree.

"This issue is important to the American people. Let's face it. Opening foreign markets is good for American workers and it's good for American business," said House Speaker Dennis Hastert of Illinois at news conference Tuesday. "We all know that when business does well, jobs are created."

Hastert was joined by Commerce Secretary Carlos Gutierrez (search) and representatives from pro-CAFTA Hispanic groups.

House Democrats, who traditionally oppose such free-trade agreements, say they are united in opposition. Leaders of 20 powerful labor unions on Monday wrote a letter to House Minority Leader Nancy Pelosi (search) of California, warning that Democrats who vote for CAFTA would face "real and measurable consequences for opposing labor on this issue."

"The stakes are too high for the workers of America," reads the letter. "We cannot and we will not give any Democrat a pass on CAFTA."

• Click here to read the union leaders' letter (pdf file).

Apparently getting the message, Pelosi said Tuesday that more than 90 percent of House Democrats were voting against the bill. The House Democratic leadership on Wednesday sent notice to its caucus to make sure to be present for the vote.

Opponents note that the existing free-trade deal with Canada and Mexico, the 1994 North American Free Trade Agreement (search), has not been good for American workers.

"CAFTA is an absolute failure on every count," said Rep. Barbara Lee (search), D-Calif., on Tuesday "We have learned from 10 years of failed NAFTA policies and we cannot go back and repeat those mistakes."

"We know the truth — that the promises of CAFTA are just empty rhetoric," said Rep. Jan Schakowsky (search), D-Ill.

In an effort to find votes, the White House and GOP leaders argue that a more prosperous Central America will help shore up U.S. national security by cementing democracies in the region.

"There's nothing like a stable society to fight terrorism and strengthen democracy, freedom and rule of law," Hastert said Tuesday.

House Ways and Means chairman Bill Thomas (search) of California pointed out that in the recent past, the U.S. both supported and opposed repressive Central American governments using questionable means.

Today, Thomas noted, all Central American countries are democracies with free elections, which adds to the value of a reciprocal trade agreement.

"There was a lot of attention paid to Central America. There was a lot of money spent by Americans, and there was bloodshed by Americans in Central America," Thomas said, . "And those countries that democratically elected [their] president, that are asking us collectively for help in this trade bill, will be responded to positively."

DeLay said Wednesday that President Bush may have won over one unidentified Republican congressman when he pointed out that Central American countries have contributed troops to the U.S.-British-led effort on Iraq. DeLay added that a free-trade deal may help alleviate problems associated with illegal immigration.

"It is in the national interest that CAFTA passes. It is good for our national security in supporting these fledgling democracies at our back door," DeLay said.

Officials appeared to be having some success by making promises and cutting side deals on trade issues. Democrats said they were not pleased about that.

"CAFTA supporters have resorted to toothless side deals and strong-arm tactics because they know this agreement cannot pass on its merits," said Rep. Sherrod Brown (search), D-Ohio.

"There's deal-making that goes on in the United States Congress," countered White House spokesman Scott McClellan on Tuesday. "This is a free-trade agreement that will help level the playing field for American producers and American farmers and for our products."

The leaders of all six CAFTA nations recently visited members of Congress and spoke to Hispanic and other groups to promote the deal. Whether their arguments were in vain will be determined this week.

The House vote is expected before Congress leaves Friday for its six-week summer break.

The Associated Press contributed to this report.