China’s "breathtaking expansion” of its strategic and nuclear arsenal is a quickly escalating risk for the United States, the head of U.S. Strategic Command plans to tell lawmakers at a closed-door hearing on Tuesday.

China’s first test of an intercontinental ballistic missile-launched hypersonic glide vehicle last July is a "technological achievement with serious implications for strategic stability,” Adm. Charles Richard wrote in prepared testimony posted on the website of the House Defense Appropriations subcommittee.

The hypersonic vehicle flew 40,000 kilometers (25,000 miles) for more than 100 minutes, Richard wrote in the testimony — the most detailed U.S. account of the test to date. It was "the greatest distance and longest flight time of any land attack weapon system of any nation to date,” according to the testimony. Richard gave similar testimony to both the House and Senate Armed Services Committees last month.