Chief negotiators from countries involved in a Pacific Rim free trade initiative resumed talks Monday in Hawaii, as the 12 negotiating members attempt to reach a deal by the end of spring.

As the United States, which leads the framework, will enter full-fledged campaign mode later this year for the 2016 presidential election, May is seen as an effective deadline for concluding the five-year-old Trans-Pacific Partnership talks. But gaps still remain over contentious issues, including intellectual property and establishing unified rules for fair business competition.

The prospect is uncertain also due to little progress made during recent bilateral negotiations between Japan and the United States — the two largest economies in the TPP — as well as the delay in debating a bill to grant President Barack Obama fast-track authority to sign trade deals.