A top U.S. House Democrat is warning of signs that Japan is considering steps to devalue its currency, a move that could hurt the ailing U.S. auto industry, and he urged President Barack Obama to step up pressure on the Japanese government.

House Financial Services Chairman Barney Frank, D-Mass., echoing concerns of U.S. auto makers and their congressional allies, called on Obama this week to pressure Japan to resist the temptation to devalue the yen.

Japan is facing increasing pressure from its industries to devalue the yen to stimulate Japanese exports "at the expense of the U.S. and other economies," Frank and Rep. Sander Levin, D-Mich., chairman of the House trade subcommittee, wrote in a letter to Obama this week. The U.S. congressmen added that recent statements by "several senior Japanese officials" indicate Japan is considering such a move.

"These statements are deeply disturbing, given the fragility of the global economy today and Japan's recent history of massive currency market interventions," the U.S. lawmakers wrote.

While calling the U.S. and Japan "close friends and key allies," Frank and Levin urged Obama to send a strong message to Japanese Prime Minister Taro Aso about the importance of market forces in determining exchange rates.

Obama and Aso met at the White House on Tuesday. A White House spokeswoman did not immediately respond to a request for comment Wednesday.

U.S. auto makers have heavily lobbied the U.S. government to take a tough stance against Japan on possible currency manipulation. Cars are one of Japan's top exports, and auto makers argue the U.S. auto industry would be further crippled by any attempts by Japan to devalue the yen.

"It is something that is a very high concern," said Steve Collins, president of the Automotive Trade Policy Council, an association representing General Motors Corp. (GM), Ford Motor Co. (F) and Chrysler LLC. "The magnitude of the impact would equal or certainly challenge the impact of the stimulus (package) and the loan request that the auto companies have sought and secured from the government to get through this slump."

Michigan's two Democratic senators, Debbie Stabenow and Carl Levin, wrote to Treasury Secretary Timothy Geithner and National Economic Council Director Lawrence Summers urging them to fight any attempts by U.S. trade partners, including Japan, to manipulate currency rates.

Lowering a currency's value, they said, would provide a "subsidy" to a particular country's firms, "enabling them to undercut American businesses and workers," the senators wrote.

-By Josh Mitchell, Dow Jones Newswires; 202-862-6637; joshua.mitchell@dowjones.com