WASHINGTON » Top trade officials from the United States and 11 other Pacific Rim countries are headed for an extended day of talks today, a sign that negotiators may be nearing a final agreement on the controversial Trans-Pacific Partnership deal.

U.S. Trade Representative Michael Froman and his counterparts, representing countries that include Japan, Canada, Mexico and Australia, began meetings Wednesday in Atlanta in the hope that they could work out sharp differences over dairy, drugs and autos to clinch a deal on the elusive trade accord.

There were no official updates on any progress, but people monitoring the talks at a downtown hotel said Thursday the meetings were likely to stretch into a third day. “No known breakthroughs, but there is reason for optimism still,” said Alan Wolff, a senior counsel at Dentons law firm in Washington, D.C.

Speaking from Atlanta, Wolff, U.S. deputy trade representative during the Carter administration, said he saw a good chance the parties would reach consensus this week.

The last round of negotiations, on Maui about two months ago, was a major disappointment. Some were surprised that the issue over where auto parts are made would be such a sticking point.

Wolff said there were “no hidden issues” this time and that the trade ministers arrived in Atlanta with strong public backing from President Barack Obama and other nations’ leaders.

The Trans-Pacific Partnership is a sweeping deal that would more closely link nations that combined make up 40 percent of the world economy.

Officials have been negotiating for several years on hundreds of tariff items and 29 chapters that cover rules on labor, state-owned enterprises, e-commerce and other areas of investment and trade.