The chief trade negotiators from the 12 Pacific Rim countries drafting the Trans-Pacific Partnership free trade accord will end their working-level talks Friday in Singapore, setting the stage for a crucial ministerial gathering this weekend.

After missing their goal of sealing the pact last year, the ministers will try to reach a broad agreement on politically sensitive issues during a four-day conference through Tuesday. But many issues, including tariff removal, remain unresolved.

During the five-day chief negotiators' talks ahead of the high-level conference, Japan underwent almost six hours of intense questioning by the other negotiators over its refusal to open up its agriculture market.