A technical glitch forced South Korea to abort liftoff of its first rocket into space Wednesday, delaying a launch that threatened to heat up tensions with rival North Korea even as they joined in mourning the death of an ex-president who pushed tirelessly for reconciliation.

Both Koreas are eager to develop their space programs, and had aimed to launch satellites into space this year. Pyongyang beat Seoul to it with the April liftoff of a three-stage rocket it claimed sent a communications satellite into orbit, although experts doubt it really succeeded.

Washington, Tokyo and others called it a disguised a test of its long-range missile technology since the same rocket can be used to fire off a missile. The U.N. Security Council condemned the launch, saying it was a violation of resolutions banning the North from ballistic missile-related activity.

The South's planned launch could prove a setback to recent signs of easing tensions, marked by a meeting this month between North Korean leader Kim Jong Il with former President Bill Clinton, and the releases of two American journalists and a South Korean technician from the North's custody. The North this week also agreed to resume some joint tourism and industry projects with the South.

As South Korea geared up to put its new rocket on the launchpad, North Korea warned that it would be "watching closely" for the international response to Seoul's launch.

"Their reaction and attitude towards South Korea's satellite launch will once again clearly prove whether the principle of equality exists or has collapsed," a spokesman for the Foreign Ministry told North Korea's official Korean Central News Agency.

South Korea's launch was set for Wednesday from the Naro Space Center off the southern coast, but was abruptly aborted less than eight minutes before liftoff, senior Science Ministry official Lee Sang-mok said.

The two-stage rocket, called the Naro and built with Russian help, would have been South Korea's first satellite launch from its own territory.

South Korean and Russian scientists were investigating the malfunction that forced officials to stop the launch, and Russian scientists believed another attempt could take place within days, Lee said. He said trouble with a high-pressure tank that helps operate valves in the launch vehicle may have been the problem.

Despite the North's objections, U.S. and South Korean officials say the two rocket launches cannot be compared, noting that South Korea has carried out the process transparently, and for peaceful purposes, while the North has not abided by its international commitments.

The two Koreas remain in a state of war since their conflict ended in a truce, not a peace treaty, in 1953. Relations have been tense since President Lee Myung-bak took office in Seoul in February 2008, abandoning late ex-President Kim Dae-jung's "Sunshine Policy" of encouraging reconciliation with aid.

This week, North Korea put its army on "special alert" as the U.S. and South Korea held joint military exercises in the South. Washington and Seoul say the annual computer-simulated war games, which began Monday, are purely defensive. But North Korea's Foreign Ministry warned they were "aggravating" tensions on the Korean peninsula.

"Lurking behind them is a dangerous scheme for aggression to mount a pre-emptive nuclear attack," the ministry said in a statement carried by KCNA.

Yet in a further sign of a thaw, North Korean diplomats from the country's U.N. mission have requested a meeting later Wednesday with New Mexico Gov. Bill Richardson, his office said. Richardson was U.N. ambassador during Clinton's administration. In the 1990s, Richardson, then a congressman, went to North Korea twice to secure the release of detained Americans.

Also, Kim Jong-Il sent condolences to the family of former leader of the South, Kim Dae-jung, who died Tuesday at age 85 after a lifetime of fighting for democracy and reconciliation on the Korean peninsula. The two leaders met in a historic summit in 2000 — the first between the two Koreas.

"The feats he performed to achieve national reconciliation and realize the desire for reunification will remain long with the nation," KCNA quoted the North Korean leader as saying.

North Korean officials have conveyed their wish to send a delegation to pay their respects to Kim, lawmaker Park Jie-won, a former aide to Kim Dae-Jung, said Wednesday.

Pyongyang has only ever dispatched a condolence delegation for one other South Korean: the industrialist Chung Ju-yung, founder of the Hyundai Group, which funded the first inter-Korean joint projects.

The South Korean government was discussing whether to allow the North's delegation to visit, Unification Ministry spokeswoman Lee Jong-joo said.

Thousands lined up in Seoul to lay white chrysanthemums before a portrait of the longtime dissident-turned-president, who won the Nobel Peace Prize in 2000 for his reconciliation efforts.

"It feels as if my heart is being torn," Yang Young-sim, a 58-year-old housewife, said between sobs. "He is a man who has devoted his entire life to Korea's democracy."

North Koreans in Pyongyang were also mourning Kim, according to the Choson Sinbo, a Tokyo-based newspaper viewed as a mouthpiece for the North Korean government.