SEOUL, South Korea (AP) _ The United States and South Korea will begin two weeks of joint military exercises Monday that are designed to boost preparedness for an attack by North Korea, military officials from both countries said Wednesday.

The annual exercise will be the allies' first joint war games this year. About 13,000 U.S. soldiers, some of them based outside Korea, and more than 57,000 South Korean troops will participate.

The exercise simulates war conditions with mock chemical weapons attacks on the capital, Seoul's Defense Ministry said.

Some 37,000 U.S. troops are stationed in South Korea, and the armed forces of the two countries hold several joint exercises each year.