(Updates with agreement on dates of event)
By James Pearson
SEOUL, Feb 5 (Reuters) - North and South Korea agreed on Wednesday to allow some families separated by the 1950-53 Korean War to hold brief reunions, despite a campaign by Pyongyang that Seoul cancel planned war games with the United States.
Any kind of agreement between the two rivals is rare, and in the past unpredictable North Korea has withdrawn permission for the event at the last minute.
A meeting of officials from North and South Korea agreed the reunions will take place on Feb. 20 to 25 in Mount Kumgang, just north of the border, South Korea's Unification Ministry said. At previous reunions, about 100 families have been allowed to meet relatives on the other side for fleeting moments before they are sent back to their respective homes.
Officially North Korea has not linked the reunions with its demand for the cancellation of the annual military exercises by the U.S. and South Korean militaries scheduled to begin this month.
But officials in the South say the intention is clear, and that Seoul will not fall in line.
"The drills have been conducted annually and they simply cannot be an issue for us as far as the reunions are concerned," said a South Korean government official involved in dealings with the North, who spoke on condition of anonymity.
In recent weeks, North Korean diplomats have given rare media interviews and press conferences that have reiterated calls from Pyongyang's top ruling bodies to end the annual military drills.
It was unlike North Korea's usual threats and aggressive tone used with the South but that does not mean Pyongyang has changed, analysts said.
"There is no more seriousness behind this offer than others Pyongyang has advanced," said Andrea Berger, a research fellow at the Royal United Services Institute in London who interacts regularly with North Korean officials.
"North Korea has not yet made clear that the significant military restraint it is demanding on the South Korean side would be matched by military restraint on its own part."
The North's offer to allow the family reunions has been welcomed both by its sole major ally, China, and the United States, who were also on opposing sides in the Korean War.
The war left millions of families divided, with free private travel across the border and communication, including phone calls, banned.
More than 70,000 South Koreans have been seeking to meet lost family members at family reunions. The successful ones are chosen by lottery.
Tensions on the Korean peninsula soared last year as Pyongyang reacted angrily to tightened U.N. sanctions imposed in response to its latest nuclear test.
That was followed by a period of aggressive rhetoric from the North that warned of nuclear war should joint U.S.-South Korean drills continue - a threat the United States responded to with long-range nuclear bomber sorties over the peninsula.
"Their tone this year is different; they're saying 'please don't do this', as opposed to in the past when they threatened military action if drills went ahead," said Kwak In-su, a researcher at the Seoul-based Institute for National Strategy and a former North Korean spy who fled to the South in 1995.
"They're putting on a show but at the same time they really want some changes - it's a mixed bag," he added.
North Korea's intentions are always difficult to read, and the relative lack of understanding surrounding Kim Jong Un, the third of his family to rule the country, has made the situation even more complex. Kim's government ordered the execution of his uncle, viewed as the number two leader in North Korea, last year and has purged officials related or linked to him.
The impending war drills could provide an excuse for North Korea to do call off the reunions, said Berger, the analyst.
"The scheduling of family reunions highlights one of the side effects of decades of North Korean allergic reactions to military exercises," she said.
"To avoid the risk that Pyongyang's objections to joint drills cause such engagement to collapse from one side, Seoul and Washington intentionally try to conclude or fulfil bilateral agreements before exercises start." (Additional reporting by Jumin Park and Michelle Kim; Editing by Jack Kim and Raju Gopalakrishnan)