The senior US trade official says progress has been significant in talks to secure a Pacific-wide trade deal by the end of the year.
The leaders of the 12 countries involved in the Trans-Pacific Partnership (TPP) talks will meet on the sidelines of the Asia Pacific Economic Co-operation summit in Bali on Tuesday to try to help overcome outstanding issues.
Some commentators have questioned whether a deal can be done by the year's end without the involvement of US President Barack Obama who has cancelled a visit to the region because of the government funding crisis in Washington, missing the APEC summit.
New Zealand Prime Minister John Key will chair the TPP meeting in Mr Obama's place.
US Trade Representative Michael Froman said significant progress had been made in the past few days and insisted the TPP remains on track.
"We spent a great deal of time this week working on TPP. The TPP countries are strongly committed to working to conclude negotiations this year."
Radio New Zealand's economics correspondent says negotiations are understood to be moving slowly on several sensitive issues, including intellectual property and access for agricultural products.
US Secretary of State John Kerry, who is standing in for the president at APEC, says the US is not neglecting its responsibilities, including those in Asia, and that the meeting remains a premier forum for fostering more free trade.
"I do want to make clear, none of what is happening in Washington diminishes one iota our commitment to our partners in Asia, including our efforts to promote trade and investment throughout the region," he said.
The TPP is under negotiation by the United States, Australia, New Zealand, Japan, Singapore, Malaysia, Brunei, Vietnam, Chile, Canada, Mexico and Peru.