US lawmakers expressed concern over Japan’s interest in joining free trade talks with the US in a move they claim could hurt the country’s auto industry.

Four dozen Democratic lawmakers urged President Barack Obama to maintain US tariffs on Japanese cars and trucks amid fears from the so-called Detroit Three – the US’ largest automakers – including Ford Motor Co., General Motors and Chrysler Group – of losing more sales to Japanese imports, Reuters reports.

Japanese Prime Minister Shinzo Abe announced that Tokyo is interested in joining talks on a US-led Trans-Pacific Partnership, a proposed free trade pact between the US and 10 other countries.

“In an industry with razor-thin profit margins, the elimination of the 2.5% car tariff (as well as the 25% truck tariff) would be a major benefit to Japan without any gain for a vital American industry, leading to more Japanese imports, less American production and fewer American jobs,” the lawmakers said in a letter to Obama.

The 48 lawmakers issued the “sound alarm” about Japan’s participation in the TPP, said Representative Sander Levin, the top Democrat on the House of Representatives Ways and Means Committee.

Levin also said he was “skeptical” over whether negotiations could tear down regulatory and other non-tariff barriers that have long kept American autos out of Japan’s market, Reuters reports.

“The Japanese auto market is more impenetrable, the history of formidable barriers and imbalanced trade is longer,” the lawmakers said.

Japan has been seeking to join talks on the TPP as Prime Minister Shinzo Abe pushes for his economic policy aimed at reviving the stagnant economy.