WASHINGTON – Japan still has a long way to go before it can say its markets are open, the top U.S. trade official said on Friday.

Trade Representative Michael Froman said he hopes Japan’s recent entry into the Trans-Pacific Partnership, or TPP, free trade negotiations will provide opportunities to tear down those barriers.

“I think we all bear the scars of trying to open Japan’s market in the past,” Froman told reporters at a briefing, acknowledging the “historical difficulties” in the trade relationship.

In their long history of trade disputes, the U.S. has alleged Japanese markets are closed to imports because of restrictive practices that are tolerated or even encouraged by the government. At the same time, Japan has relied heavily on exports as an engine of growth for its sluggish economy.

Froman mentioned autos specifically — one of the thorniest issues in trade relations.

“Right now, all foreign penetration of the Japanese auto market is 6 percent, and so I think everyone believes there is a long way to go before we can really say the Japanese market is open,” he said.

Japan formally joined the United States and 10 other Asia-Pacific nations in negotiations to create a major new trade bloc during the 18th round of talks in Malaysia last month. With the addition of Japan, the 12 countries would account for some 40 percent of world trade volume.

The other 10 countries are Australia, Brunei, Canada, Chile, Malaysia, Mexico, New Zealand, Peru, Singapore and Vietnam.

Froman was speaking ahead of a trip to Japan and Brunei that will revolve around trade negotiations. The next round of talks is in Brunei from Aug. 23-30.

Some in Congress are urging the Obama administration to link the reduction of American auto tariffs to the opening of the Japanese auto market in the TPP talks.