SAN DIEGO - The United States and eight other Pacific Rim countries have opened another round of talks aimed at producing a new trade deal.

Negotiators trying to create the Trans-Pacific Partnership Free Trade Agreement have met about a dozen times over the past three years.

The talks include Australia, Brunei, Chile, Malaysia, New Zealand, Peru, Singapore and Vietnam, with Canada, Mexico and possibly Japan expected to join.

The proposed partnership was largely unknown outside trade circles until last fall when Prime Minister Stephen Harper signalled a desire to join the nine-member club.

Ottawa lobbied hard to be admitted and it paid off at a recent G20 gathering in Mexico when it was announced that Canada would be invited.

But Canada's admission must first be approved by all the other countries and U.S.

President Barack Obama said in November he was optimistic an agreement would be reached this year, before Mexico and Canada were slated to join.

About 100 protesters peacefully demonstrated outside a downtown hotel where the talks opened Monday. Critics said the talks threatened climate change laws, regulation of financial markets, labour rights and environmental and health protections.

Critics say the process has been shrouded in secrecy. Last week, two-thirds of House Democrats wrote to U.S. Trade Representative Ron Kirk _ the White House’s top trade official _ complaining they were being left out of the loop on the pact.

U.S. officials insist they have been as open as they have ever been on a trade agreement. They say making public their negotiating positions would undercut their leverage in the talks with other countries.

“We’re trying to be as transparent as possible,” responded Michael Masserman, executive director of export policy at the U.S. Commerce Department. “Lots of sensitivities in the (intellectual property) negotiations.”

Unlike past negotiations with Europe and India, the Harper government has not released a cost-benefits study to speculate how much could be gained and at what price.

As a latecomer, Canada has had to accept all that has already been agreed to by the TPP partners, although Harper said he believes the talks are still in the early stages.

John Manley, a former Liberal trade minister who now heads the Canadian Council of Chief Executives, said once the U.S. joined the club, Canada could no longer sit out.

The reason, he said, is more to do with protecting what Canada has than what it can gain through greater access to markets like Vietnam or even Australia.

Given the degree of economic integration in North America, Canada sitting out from a trade deal that includes the U.S. and Mexico could disrupt existing supply chains.

"It's partly defensive for sure. The risk of disrupting the U.S. relationship is not one to be ignored," he said.

— with files from The Associated Press