The Foreign Ministry issued on Thursday its highest travel warning for Kuwait and Saudi Arabia, urging Japanese nationals to evacuate as a U.S.-led war against Iraq appears imminent.

The warning applied to Kuwait and the Khafji district of northeastern Saudi Arabia. The ministry also stepped up its warning for Riyadh, the Saudi capital, the outskirts of Riyadh and the western region of the country, urging travelers to put off trips to those areas.

If U.S.-led forces take military action against Iraq, airports may be closed and flights canceled, making it difficult for people to leave the two countries, according to the ministry.

If attacked, Iraq has said it will attack Kuwait because there are U.S. military bases there.