U.S. chipmaker Nvidia helped China’s DeepSeek hone artificial intelligence models that were later used by the Chinese military, the chairman of a U.S. House of Representatives committee said in a letter on Wednesday.

DeepSeek shook markets early last year with a set of AI models that rivaled some of the ​best offerings from the United States but were developed with far less computing power, fueling concerns in ‍Washington that ⁠China could catch up with the U.S. in AI despite U.S. restrictions on the ‍sale of high-powered computing chips to China.

In a letter to U.S. Commerce Secretary Howard Lutnick, Rep. John Moolenaar, a Michigan Republican who chairs the House Select Committee on China, said documents obtained by the committee from Nvidia showed the achievement came after extensive technical assistance from Nvidia.