WASHINGTON -- Peru, an Andean nation of 28 million people, seems an unlikely political threat to Democrats.

But it could split the party this week, as the full House of Representatives considers the first vote on a free-trade agreement since the 2006 election, when Democrats won control of both chambers of Congress.

The party leadership supports a Peru pact because it contains stronger labor and environmental standards than past agreements. Yet many rank-and-file Democrats, including freshmen lawmakers who assailed the dangers of free trade for American workers on the campaign trail last year, are skeptical.

It's an especially sensitive issue in Pennsylvania, which has lost nearly 200,000 manufacturing jobs since 2000.

"Fundamentally, these bills have hurt Western Pennsylvania," said Rep. Jason Altmire, D-McCandless, a freshman who had been critical of his predecessor, Republican Melissa Hart of Bradford Woods, for supporting the Central American Free Trade Agreement, or CAFTA.

"But I don't want to be in the position of voting against every trade agreement because it's a trade agreement," he added. "I want to be thoughtful and deliberate and take a look on a case-by-case basis to see if it's going to affect our region.

Mr. Altmire said he hasn't decided how he'll vote, but he was heartened by changes made in May, when Democratic leaders reached a compromise with the Bush administration to include the standards of a 1998 International Labor Organization declaration in the core language.

The revised agreement also compels Peru to abide by several multilateral environmental accords. And it will become the template for free-trade agreements with Panama, Colombia and South Korea.

"Leadership worked very, very hard to make this a very different agreement," said Rep. Allyson Schwartz, D-Philadelphia.

Ms. Schwartz is a member of the House Ways and Means Committee, which approved the Peru accord last week and sent it to the full House. In August, she traveled with Rep. Charlie Rangel, D-N.Y., the committee chairman, to Peru. She said the nation's president and legislative leaders gave assurances that they would uphold the agreement's new standards.

The AFL-CIO, normally a vocal critic of free trade, is remaining neutral on the Peru issue, providing cover to some Democrats.

But other unions are still strongly opposed.

"The labor and environmental standards are an improvement," said Don Siegel, vice president for the 3rd District of the International Brotherhood of Electrical Workers, based in Coraopolis. "But there are no assurances that they would be enforced."

Rep. Mike Doyle, D-Forest Hills, said last week he likely would oppose the agreement because of the Bush administration's poor history of enforcement, a concern echoed by Mr. Altmire and Ms. Schwartz.

"I just don't trust this president to enforce any of those [labor and environmental] provisions," Mr. Doyle said.

Gretchen Hamel, a spokeswoman for the office of the U.S. trade representative, argued that the administration has a strong record of upholding standards. She noted that an agreement approved last year with Oman still hasn't gone into effect because the Middle Eastern country hasn't addressed some intellectual property issues.

The United States is Peru's biggest trading partner, purchasing more than 20 percent of the South American country's imports last year, according to the CIA world fact book. But Peru ranks 45th among American trade partners. Its 2006 GDP of $186 billion is a fraction of the size of the U.S. economy.

"Peru has very little ability to buy finished U.S. products from places like Western Pennsylvania," said Lloyd Wood, a spokesman for the American Manufacturing Trade Action Coalition. "Peru exports twice as much to us as we export to them. This agreement is just going to exacerbate the problem."

But a May 2006 report from the U.S. International Trade Commission predicts that exports with Peru would increase by $1.1 billion under the free-trade accord, while imports would increase by half that figure.

"It will dramatically increase exports to Peru," said Rep. Phil English, R-Erie, who voted for the agreement last week in the Ways and Means Committee. "The Peruvians have bent over backward to accommodate us."

Ms. Schwartz argued that it would open up the country's sizeable mining industry to heavy equipment from the United States.

She's involved with gathering support this week before the House vote.

The agreement, which also faces Senate approval, has a strong chance of passing, with most Republicans in favor. But Democratic leaders are reluctant to predict whether it would garner majority support in their party.

Brendan Daly, a spokesman for House Speaker Nancy Pelosi, D-Calif., said she expects a "strong vote."

Mr. Altmire said he isn't feeling any pressure, although there is a lot of anti-trade sentiment in his district, which stretches from Murrysville in the southeast to Farrell, Mercer County, in the northwest.

"This is my first major trade agreement," he said, "so I take it seriously."