Updated

North Korea agreed Tuesday to allow South Koreans working in a joint industrial zone in North Korea to cross the border after Pyongyang's move to cut the last military hot line to Seoul left hundreds stranded overnight, officials said.

North Korea put its troops on alert and cut the hot line Monday as the American and South Korean militaries began joint maneuvers. The communist regime warned that even the slightest provocation could trigger war during the 12-day drills.

The North stressed that provocation would include any attempt to interfere with its impending launch of a satellite into orbit. U.S. and Japanese officials fear the launch could be a cover for a test of a long-range attack missile and have suggested they might move to intercept the rocket.

"Shooting our satellite for peaceful purposes will precisely mean a war," North Korea's military threatened in a statement carried by the official Korean Central News Agency. Any interception attempt will draw "a just, retaliatory strike," it said.

The North has been on a steady retreat from reconciliation since President Lee Myung-bak took office in the South a year ago. After Lee said the North must continue dismantling its nuclear program if it wants aid, Pyongyang cut ties, suspended joint projects and stepped up its belligerence rhetoric.

"The danger of a military conflict is further increasing than ever before on the Korean peninsula because of the saber rattling which involves armed forces huge enough to fight a war," the North's news agency warned as Pyongyang put its armed forces on standby for combat.

The North condemns the exercises as a rehearsal for invasion and last week threatened danger to South Korean passenger planes flying near its airspace if the maneuvers went ahead.

The exercises are annual drills the two nations have held for years, are "not tied in any way to any political or real world event," Gen. Walter Sharp, the U.S. commander, said in a statement Monday. The U.S. has some 28,500 military personnel in South Korea.

In Washington, State Department spokesman Robert Wood reiterated that the drills "are not a threat to the North. What is a threat to the region is this bellicose rhetoric coming out of the North."

Analysts say North Korea's heated words are designed to grab President Barack Obama's attention. With South Korea cutting off aid, the impoverished North is angling for a diplomatic coup of establishing direct ties with the U.S., said Kim Yong-hyun, a North Korea expert at Seoul's Dongguk University.

For weeks, the North has said it is forging ahead with plans to send a communications satellite into space — a launch that U.S. and Japanese officials say would violate a U.N. Security Council resolution banning the North from ballistic activity. That decree came after the North test-fired a long-range missile and conducted an underground nuclear weapon test in 2006.

Analysts have said the launch could come late this month or in early April, around the time North Korea's new parliament, elected Sunday, convenes its first session with leader Kim Jong Il at the helm.

In Seoul, Obama's special envoy on North Korea, Stephen Bosworth, urged Pyongyang not to fire a missile, which he said would be an "extremely ill-advised" move.

"Whether they describe it as a satellite launch or something else makes no difference," Bosworth said after talks with his South Korean counterpart on drawing Pyongyang back to international talks on the North's nuclear disarmament.

South Korea's Defense Ministry spokesman, Won Tae-jae, played down the North's threats as "rhetoric."

Hundreds of South Koreans were stranded overnight in the northern border town of Kaesong after Pyongyang severed the last communications link between the two governments. Cutting the hot line for the duration of the 12-day U.S.-South Korean maneuvers leaves the two Koreas without any means of quick, direct communication at a time of high tension.

The two Koreas also use the hot line to coordinate the passage of people and goods through the heavily fortified Demilitarized Zone, and its suspension shut down traffic Monday and stranded about 570 South Koreans who work at a joint industrial zone north of the border.

The North agreed early Tuesday to reopen the border to South Korea's Kaesong employees, Unification Ministry spokesman Kim Ho-nyeon said in Seoul.

North and South Korea technically remain in a state of war since their 1950-53 conflict ended in a cease-fire, not a peace treaty.