US officials say Canada and Mexico have both expressed interest in joining a US-backed trans-Pacific trade initiative.
The move boosts US president Barack Obama's ambitious agenda for the annual Asia-Pacific economic (Apec) summit.
The White House press secretary issued a statement saying Mr Obama welcomed Canadian Prime Minister Stephen Harper's indication his government would begin talks on joining the so-called Trans-Pacific Partnership.
It said that together with similar announcements by Japan and Mexico, the news shows the "broadening momentum and dynamism" of the effort to work toward an eventual region-wide free trade zone.
The US trade representative, Ron Kirk, also welcomed the positive overtures from America's "neighbours and largest export markets".