US trade officials hope to sell lawmakers on a 12-nation Pacific trade pact that is about to be formally signed in New Zealand, even as US elections look likely to delay congressional action.
"Momentum for passage is growing," US Trade Representative Michael Froman told reporters, pointing to support from US business and agriculture groups for the Trans-Pacific Partnership (TPP).
However, congressional leaders have indicated they will put off a vote on the deal agreed among member countries last year until after November presidential and legislative elections.
Mr Froman said Barack Obama's administration would work with congress to "determine the most conducive pathway" but declined to give a date for legislative action because once the agreement is officially delivered to Congress, a clock begins ticking that requires lawmakers to act.
"It's imperative we move forward," Froman said, pointing to a "significant cost" of delayed action.
Trade ministers from the TPP's partner countries have been invited to formally sign the deal in Auckland tomorrow.
Yesterday Mr Obama met Republican leaders from both the Senate and House of Representatives on legislative priorities for the year, including TPP passage.
Speaker of the House Paul Ryan said after the meeting that he and Senate Majority Leader Mitch McConnell "also discussed a number of concerns that lawmakers have raised about the substance of TPP that must still be addressed".
The 30-chapter TPP agreement includes elimination and reduction of about 18,000 tariffs on industrial and agricultural goods, including textiles and clothing; rules on trade in services and financial goods; and commitments on the free flow of internet and digital commerce.
It sets out rules for patents, trademarks and other intellectual property across the trade zone, including specific provisions about pharmaceuticals, and enforces labour and environmental standards.