Canada and Mexico want to join talks to forge a free trade area in the Asia-Pacific region, giving a significant boost to the U.S.-led initiative to foster economic growth by tearing down trade barriers.
Japan, the world's third-largest economy, said earlier it would like to join.
Canadian Prime Minister Stephen Harper said on Sunday he was encouraged to take part by U.S. President Barack Obama.
We looked at the outline of the criteria set by the partnership and they are all criteria that Canada can easily meet. So it is something we're interested in moving forward on, Harper said at the Asia-Pacific Economic Cooperation summit of 21 nations in Hawaii.
A Mexican official told Reuters his government would ask on Sunday to join the talks.
The proposed Transpacific Partnership pact now includes nine countries -- the United States, Australia, New Zealand, Singapore, Malaysia, Brunei, Chile and Peru -- that have committed to what they call a high-standard trade agreement.
They must approve new applicants. The TPP goal is to complete a detailed framework in 2012 and adding new members could slow the timetable.
Japan strengthened the significance of the talks on Friday when it expressed its interest in joining the pact, which analysts see as important to ensuring the United States maintains a strong economic presence in the region as China continues to rise.
With Japan included, the proposed economic pact would be about 40 percent larger than the 27-nation European Union.
Mexican Economy Minister Bruno Ferrari told Reuters on Friday that the TPP potentially offered his country an attractive opportunity to boost growth.
The United States and Canada have been free trade partners since the late 1980s, first under a bilateral agreement and then the North American Free Trade Agreement that brought in Mexico in 1994.
But negotiators are addressing many issues in the TPP talks that have arisen since NAFTA went into force. Those include the role of state-owned enterprises in international trade, government innovation policies and cross-border data flows.
(Reporting by Rachelle Younglai and Doug Palmer; Editing by John O'Callaghan)