LEESBURG, Va. -- With 1,350 employees in its five U.S. factories, New Balance is proud it still produces 7 million pairs of shoes each year at its plants in Maine and Massachusetts, the last major athletic-footwear company that still has manufacturing jobs in the United States.

But the company says those jobs could disappear if the U.S. scraps its tariff on athletic footwear coming in from Vietnam.

It's part of the mounting anxiety over the Trans-Pacific Partnership, the largest trade pact proposed in U.S. history. And as 400 negotiators from nine countries met privately at a Northern Virginia golf course last week in an attempt to finalize details, New Balance officials weren't the only ones fretting.

Autoworkers feared the loss of 26,500 domestic jobs and said the production of American cars would fall if Japan joins the pact and the United States drops a 2.5 percent tariff on Japanese cars, making them cheaper to buy.

Doctors worried that it will be harder to get medicines to fight AIDS and other diseases in developing countries if U.S. negotiators insist on extending patents for pharmaceutical companies.

And many members of Congress and other critics lamented that such big decisions were being made in secret at a luxury resort far from public view.

But while opponents derided the new trade pact as "NAFTA on steroids," a reference to the North American Free Trade Agreement passed by Congress in 1993 that opponents say led to U.S. jobs moving to Mexico, backers predicted the Trans-Pacific deal would increase U.S. exports, create more jobs and lower prices for American consumers.

Negotiations include the United States, Australia, Brunei, Chile, Malaysia, New Zealand, Peru, Singapore and Vietnam. Mexico and Canada will soon formally join the talks, bringing the total membership to 11 countries.

Japan already has expressed interest in participating, and China is regarded as a potential partner down the road.

"It's NAFTA on steroids in terms of its geographic scope, its economic scope and the new powers it gives to corporations," said Arthur Stamoulis, a critic of the trade deal and executive director of the Citizens Trade Campaign, a coalition that includes labor and environmental groups.

The deal is an attempt to get the United States to cash in on a region that accounts for more than 40 percent of all international trade.

In addition to eliminating many tariffs, negotiators hope to reduce regulations and the cost of trade, to promote more digital and "green" technology, and to come up with rules on a wide variety of topics, addressing everything from sanitary standards to customs procedures to environmental issues.

The Asia-Pacific region is an increasingly important market for U.S. businesses, accounting for $775 billion in exports in 2010, a 25.5 percent increase from just a year earlier.

In Washington state, where at least one of every three jobs is tied to international trade, the pact presents "a tremendous opportunity" to boost trade with the Asia-Pacific region, which already accounts for nearly 70 percent of the state's exports, said Eric Schinfeld, president of the Washington Council on International Trade.

He predicted the pact would particularly help the state's apparel industry and some of its biggest companies, including Nordstrom, REI, Costco and Starbucks, helping them export more products. And with its proximity to the region, the state would benefit from more imports passing through on their way to final destinations.

"That's big business for our ports," Schinfeld said. "Asia-Pacific is a really big deal for us."

In a speech in Russia on Sept. 8, Secretary of State Hillary Rodham Clinton said the deal marked a major push by the Obama administration to open new foreign markets and reduce barriers to trade, which she said would lead to "more and better growth."

She said it's part of the president's plan to advocate for U.S. businesses and to double the nation's exports during a five-year period, from the year Obama took office in 2009 to 2014.

"American companies are eager to invest more in Asia," Clinton said.

Negotiators concluded their 14th round of talks Saturday, wrapping up 10 days of meetings in Leesburg, Va. The talks are expected to continue into next year, with the next round Dec. 3-12 in Auckland, New Zealand.