Japan and the United States failed to narrow gaps over the Trans-Pacific Partnership in a week of meetings that ended Tuesday, but the two sides may hold additional working-level talks later this month, Japanese officials said.

"I know our time is limited," Hiroshi Oe, deputy chief negotiator for the free trade pact, told reporters. He pledged more efforts to settle market access issues through consultation with his U.S. counterpart, acting Deputy Trade Representative Wendy Cutler.

Trade negotiators met amid growing speculation that the two economies could soon strike a deal to bring the 12-country initiative into existence.

"We recognize Japan and the United States will have to close a deal on market access" before ministers from all 12 countries meet, Oe said.

Oe said he and Cutler will have to meet "at least once again" to discuss Japan's desire to retain exceptional tariffs on some agricultural produce before the two governments hold ministerial talks.

Oe declined to give any time frame for a meeting between TPP minister Akira Amari and U.S. Trade Representative Michael Froman.

Japan and the United States account for a combined 80 percent of the TPP members' economies, and their lingering differences are seen as having acted as a drag on the overall negotiations, which are nearly 5 years old.

Negotiation sources said Tokyo and Washington are trying to hold a ministerial meeting in late February at the earliest.

Takeo Mori, a senior Japanese official handling automotive trade issues, told reporters in a separate press briefing that "we were able to settle small issues mostly, but could not do so on bigger matters."

The 10 other TPP negotiating countries are Australia, Brunei, Canada, Chile, Malaysia, Mexico, New Zealand, Peru, Singapore and Vietnam.