North and South Korea were at odds Tuesday in procedural wrangling that delayed the start of the first formal meeting between the two sides in more than a year, amid tensions over Pyongyang's moves to restart its nuclear program. South Korean officials traveled to the North Korean city of Kaesong in the morning for discussions that would mark the first official meeting between the two governments since Seoul's conservative President Lee Myung-bak took office in February 2008. But the talks still had not begun more than four hours after Seoul's delegation crossed the heavily armed border. "There is no progress," said Unification Ministry spokesman Kim Ho-nyeon. "The talks have not begun yet." Kim declined to say what problems were encountered. His deputy, spokeswoman Lee Jong-joo, said earlier that liaison officers from the two sides were discussing unspecified procedural issues ahead of the formal meeting. The difficulty even getting the talks started underlines how soured the two sides' relations are. The closely watched talks follow the North's defiant April 5 rocket launch that drew international condemnation. Putting additional strain on the meeting was North Korea's recent warning that the South not join a US-led program to stop the spread of weapons of mass destruction. The North also has been holding a South Korean worker at a joint industrial complex for allegedly denouncing Pyongyang's political system. South Korea hopes to try to win the release of the detained worker during the talks. Analysts and media have speculated the North could use the meeting to raise tensions by threatening to further undermine the troubled industrial zone in Kaesong, just north of the border, if Seoul announces its participation in the anti-WMD program. Pyongyang has long denounced the program as part of what it claims are US efforts to overthrow it. "It is possible that the North might threaten to shut down the Kaesong complex if South Korea joins" the program, Cheong Seong-chang, a senior analyst at the security think-tank Sejong Institute, south of Seoul, told reporters Monday. North Korea has also been stoking tensions in the standoff over its nuclear program after the UN Security Council condemned its rocket launch. It has kicked out all international monitors of its nuclear facilities and vowed to restart them and boycott international nuclear talks. The chief of the UN nuclear watchdog, Mohamed ElBaradei, said in Beijing on Monday that the North could restart the facilities within months - a move that could lead to production of weapons-grade plutonium. Pyongyang says the UN rebuke is unfair because the rocket liftoff was a peaceful satellite launch. But the US and others believe the launch was a test of the North's long-range missile technology. Unification Ministry spokeswoman Lee said the South will "strongly respond" if North Korea takes any other steps against the detained worker beyond a fine, warning or expulsion - moves that were agreed to by both sides. There has been media speculation that the North might put the worker on trial. He was detained on March 30 for allegedly instigating North Koreans at Kaesong to flee the communist nation. Pyongyang made the surprise offer to South Korea for dialogue last week, saying only that it wants to discuss the factory park where more than 100 South Korean companies run factories and employ North Korean workers. Tuesday's talks mark the first government-to-government dialogue between the sides since Seoul's President Lee took office in February last year with a pledge to get tough with Pyongyang and its nuclear ambitions. Their ties have since rapidly strained, with the North cutting off dialogue and suspending major reconciliation projects.