By Doug Palmer

WASHINGTON (Reuters) - A California congressman at the center of a legal battle with the White House on Wednesday asked U.S. trade officials to let him sit in on negotiations in San Diego next week between the United States and other countries in the Asia-Pacific region.

"Given the immense impact that this agreement will have on many areas of the American economy, including intellectual property, I respectfully request that you allow me and certain members of my staff to be present as observers for this round of negotiations," Republican lawmaker Darrell Issa said in a letter to U.S. Trade Representative Ron Kirk.

The unusual request to join the San Diego talks on the proposed Trans-Pacific Partnership (TPP) pact, and a separate letter on Wednesday from about 130 congressional Democrats, reflect the anxiety many lawmakers are feeling about trade agreements, even though Congress last year overwhelmingly approved three such pacts -- with South Korea, Colombia and Panama.

There was no immediate comment from the U.S. Trade Representative's office regarding Issa's request.

The U.S. government is hosting the 13th round of negotiations July 2-10 on the TPP, which would create a regional free trade zone including the United States, Australia, New Zealand, Peru, Chile, Singapore, Malaysia, Vietnam and Brunei.

Those nine countries recently invited Mexico and Canada to join the talks, which are unlikely to reach an agreement before the first part of next year.

The Obama administration describes the TPP as a "21st Century" trade agreement that would set higher standards in areas from workers rights to environmental protection to intellectual property rights, as well as eliminate most, if not all, remaining tariffs between the countries.

Issa, who represents northern San Diego County, is chairman of the House of Representatives Oversight and Government Reform Committee. He has been pushing the White House to release key documents from a botched U.S.-Mexico gun-running scheme. Continued...