The leaders of the U.S., the U.K. and Australia have unveiled details of their plan to build a new fleet of nuclear-powered attack submarines as part of efforts to counter China’s growing military power and assertiveness in the Asia-Pacific region.

Under the deal, known as AUKUS, the United States intends to sell Australia three U.S. Virginia-class nuclear-powered submarines — some of Washington’s most sensitive military technology — in the early 2030s, with an option for Australia to buy two more if needed, a joint statement released Tuesday said.

In the first step of the multistage project, the U.S. and Britain will train Australian officers and engineers on operating nuclear-powered submarines.