The TPP is a regional trade negotiation that includes the United States, Australia, Brunei Darussalam, Canada, Chile, Japan, Malaysia, Mexico, New Zealand, Peru, Singapore and Vietnam, which account for nearly 40 per cent of global GDP.

In a letter circulated by Senators Joe Donnelly, D-Ind., and Charles Grassley, R-Iowa, and sent Friday to Mr Froman and Mr Vilsack, 32 Senate lawmakers said the TPP talks represent an opportunity for the United States to open new markets to US pork in the Asia-Pacific region, to expand existing markets and to establish a standard for future trade agreements.

But, the senators pointed out, a number of the TPP nations currently have highly restrictive trade barriers that limit US pork exports. Japan, for example, maintains a complex system of tariffs that reduce the volume of US pork exports, while other countries have non-tariff barriers that constrain US pork shipments.

US negotiators should insist that tariff and non-tariff barriers to US pork in each TPP country be removed, action that would prompt US pork exports to grow by more than 50 per cent within 10 years, they said.

A comprehensive TPP agreement that eliminates all tariff and non-tariff barriers to US pork is strongly supported by the National Pork Producers Council.

"Increasing pork exports are important to many more Americans than just pork producers," said NPPC President Randy Spronk, a hog farmer from Edgerton, Minnesota, who pointed out that more than 110,000 US jobs are generated by US pork exports. "So a comprehensive agreement that gives the US pork industry more access to the markets of the TPP countries will be good for pork producers and the US economy."