Chief negotiators from 12 countries involved in the Trans-Pacific Partnership initiative resumed negotiations in Washington after their leaders reaffirmed last month they will conclude an agreement as soon as possible.

The six-day working-level meeting started Sunday. This round follows a summit held Nov. 10 in Beijing, where U.S. President Barack Obama, Prime Minister Shinzo Abe and the 10 other leaders instructed officials and ministers to make concluding the free-trade deal "a top priority."

The United States, which leads the free-trade scheme, seeks to reach a broad agreement early in the new year before it enters campaign mode toward the presidential election in 2016, according to negotiation sources. However, the outlook is uncertain.

Koji Tsuruoka, Japan's top negotiator, told reporters last Thursday that many hurdles remain, suggesting it will be difficult to quickly bring the talks to the ministerial level.

"I don't think we will soon be in a situation where we are seeking political decisions" by ministers to solve difficult issues after the current chief negotiators' gathering ends, Tsuruoka said before departing for Washington.

The TPP countries are expected to discuss outstanding issues such as intellectual property and reform of state-owned firms to establish fair business competition — areas where developed and emerging economies have been at odds.

At the Nov. 10 TPP summit, the first since October last year, the leaders said the end of their nearly 5-year-old talks is "coming into focus," but in a joint statement they didn't mention a specific timeline for cutting a deal.

The TPP involves Australia, Brunei, Canada, Chile, Japan, Malaysia, Mexico, New Zealand, Peru, Singapore, the United States and Vietnam.