Japan's top trade negotiator is optimistic he can reach a deal with the United States that is essential to creating the Trans-Pacific Partnership (TPP), a free trade pact that aims to cover 12 countries including Australia.

A senior US State Department official also said on Monday a deal was within "grabbing distance" as the world's largest and third-largest economies race to conclude bilateral negotiations that cover trade in car parts and farm products.

Japan and the United States have been locked in negotiations over the TPP, a US proposal that would connect a dozen economies by cutting trade barriers and harmonising standards covering two-fifths of the world economy and a third of global trade.

"I recognise that some countries were worried about the lack of progress between Japan and the United States," said Koji Tsuruoka, Japan's chief TPP negotiator.

"However, bilateral negotiations over the past few days are a sign to everyone that we are making progress. We are now in the final stage."

A deal between Japan and the United States is considered vital to a long-delayed TPP trade pact, as their economies would account for 80 per cent of the group.

Japan's economy minister Akira Amari said on Monday access to Japan's rice market and the US auto parts market needed to be resolved for a deal to be announced.

Mr Amari and US trade representative Michael Froman were meeting in Tokyo to discuss details of a possible deal, adding momentum to multilateral efforts toward TPP.

A trade deal between Japan and the United States is within reach, the US State Department's top diplomat for Asia, Danny Russel, said.

"We are within grabbing distance of an agreement with the Japanese," Mr Russel told the Council on Foreign Relations.

Reuters