The United States and South Korea have informed North Korea of their plan to hold a joint military exercise next month, officials said.

The annual Ulchi Freedom Guardian (UFG) exercise, scheduled for August 17-27, will involve 10 000 US soldiers and an unspecified number of South Korean troops, the US military said here.

The drill involves computer-simulated war games designed to improve the allies' ability to defend South Korea from attack, it said in a statement.

North Korea, which has remained technically at war with the South since their 1950s conflict, regularly denounces such exercises as preparations for an invasion of the communist state.

Tensions have intensified since North Korea conducted missile and nuclear tests in recent weeks, triggering a new round of UN sanctions.