With U.S. President Barack Obama's visit to Tokyo approaching, Japanese and U.S. trade chiefs are set to face off again in Washington as they strive to break a deadlock in talks on a massive free trade zone in the Pacific region.

Trade observers say it is necessary to achieve an outcome, or at least to try to make progress, at the April 24 summit between Obama and Prime Minister Shinzo Abe, as failure to overcome differences on outstanding trade issues would significantly undermine Obama's trip to Japan as a state guest — which many see as a possible impetus for the stalled negotiations.

Trade officials from both countries held a preparatory session Tuesday in the U.S. capital for the ministerial talks on the thorny issue of tariffs on agricultural produce in the Trans-Pacific Partnership negotiations.