North Korea's No. 2 leader on Thursday ordered all soldiers and people to maintain a war mobilization posture to counter the threat of a U.S. attack.

"We will mercilessly repel the aggressors and achieve reunification by mobilizing" in case of a U.S. attack, Kim Yong Nam warned in a speech to thousands of government and military officials that was carried on state televison.

The speech was monitored in South Korea.

• Monitor the nuclear showdown on the Korean Peninsula in FOXNews.com's North Korea Center.

The anti-U.S. rhetoric, which came days after a breakthrough deal on ending North Korea's nuclear weapons program, is not unusual and appears directed at North Koreans as they prepare to celebrate the 65th birthday of leader Kim Jong Il on Friday.

Under the first phase of the deal reached in Beijing on Tuesday, North Korea would shut down its main nuclear reactor and allow U.N. inspectors back into the country within 60 days.

In return, it would receive aid equal to 50,000 tons of heavy fuel oil from the other countries participating in the six-party talks — the United States, South Korea, Russia, China and Japan.

North Korea regularly accuses the United States of planning to attack it. U.S. officials say they have no such intnention.

Complete coverage is available in FOXNews.com's North Korea Center.