North Korea's move to launch a long-range rocket is apparently casting a pall over inter-Korean ties and the upcoming reunions of families separated by the 1950-53 Korean War, experts said Tuesday.

North Korea said Monday that it plans to launch what it calls "a series of satellites," as it is preparing for the 70th anniversary of the founding of the Workers' Party of Korea, which falls on Oct. 10.

"The world will clearly see a series of satellites of (North) Korea soaring into the sky at the times and locations determined by the Central Committee of the WPK," the Korean Central News Agency said in a statement, without elaborating.

It marked the North's first official acknowledgment a possible rocket launch around the anniversary, raising concerns that the move, if realized, will dampen South and North Korea's hard-won conciliatory mood on the Korean Peninsula.

"The statement points to a growing possibility of the North's rocket launch ahead of the anniversary," said Cheong Seong-chang, a senior researcher at the Sejong Institute.

"The North's possible provocation would prompt the U.N. Security Council to impose sanctions against North Korea. Then, the North could use the U.N. move as an excuse to scuttle the envisioned family reunions next month," he added.

North Korea has claimed it has the right to conduct space research by test-firing what it calls satellites, but outside analysts view it as a cover for missile tests.

The North's missile and nuclear programs have flared up tension on the peninsula amid worries that it may soon develop the technology to mount a nuclear warhead on long-range ballistic missiles capable of reaching the U.S. mainland.

South Korea's defense ministry said last week that North Korea appears almost finished with construction at its rocket launch facility in Dongchang-ri on its west coast border.

In recent satellite imagery, a new 67-meter-tall gantry has been spotted on the site, which experts say can be used for the launch of long-range missiles twice the size of the 30-meter Unha-3 that was launched into orbit in December 2012.

North Korea is under heavy sanctions by the United Nations Security Council for its nuclear tests and ballistic missile launches.

The government warned Tuesday that the North's possible provocation would be a blatant violation of the UNSC resolutions, but it also remained cautious about whether the North will go ahead with a rocket launch.

"South Korea and the United States are closely collaborating to brace for every possibility, including North Korea's possible launch of a long-range missile," said a ranking official at the Unification Ministry, asking not to be named.

He said the government will not make any prejudgment over whether the North will actually fire off a rocket or whether Pyongyang's possible move would mean a breakup of the two Koreas' recent landmark deal on easing military tensions.

"It is too early to prejudge the situation," the official said.

The official also refrained from making comments on the relationship between the North's potential move and the family reunions slated for Oct. 20-26.

The North has a track record of unilaterally delaying scheduled reunion events, including in September 2013. At that time, the reunions were pushed back to early 2014.

"I think that the North's announcement has set the stage for the two Koreas to hold high-level talks at an early date," said Kim Yong-hyun, a professor of North Korean studies at Dongguk University. "South and North Korea should hold such talks as soon as possible to prevent the North from making provocations."

The two Koreas reached a landmark agreement on Aug. 25 to defuse military tension and resume the family reunions. They agreed to hold high-level talks as soon as possible without specifying the timing.

"Seoul needs to first propose for the high-level talks this time to persuade the North not to make provocations," Jeong said.

"The South need to discuss ways to resume a now-suspended inter-Korean tour program at Mount Kumgang in the North."

But some analysts said the North's late night announcement appeared to intend not to herald its rocket launch, but to gauge public opinions in the U.S. and China.

"Given Seoul's nuclear envoy is on a trip to the U.S. and the leaders from Washington and Beijing will hold a summit late this month, the North's move seemed to send a message calling for a turnaround in their policy toward North Korea," said Yang Moo-jin, a professor at the University of North Korean Studies. (Yonhap)