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A South Korean envoy who had hoped to try in person to dissuade North Korea's Kim Jong Il from pursuing a nuclear program returned home Wednesday without meeting the reclusive leader, as the North accused Washington of planning a major attack on the communist country.

South Korea had been optimistic that its delegation, led by presidential envoy Lim Dong-won, would be able to meet the North Korean leader. But instead, Lim was allowed only to meet other high-level officials, officials in the Seoul said.

Many in the South view Kim as the only figure in the reclusive country who can make any meaningful decision on the nuclear issue. There was no immediate comment from the North, which had not previously confirmed that the delegation would meet Kim.

The South Korean delegation arrived in Seoul later Wednesday after an 80-minute flight from the North.

In meetings with the South Korean envoy, Kim Yong Sun, a key aide to the North Korean leader, reiterated Pyongyang's stance that the nuclear dispute is entirely with the United States, the North's KCNA news agency reported.

In his State of the Union speech Tuesday night, President Bush denounced Kim's government as an oppressive regime that leaves its people "living in fear and starvation" and insisted the United States and other countries would not be "blackmailed" into granting concessions to North Korea because of its nuclear weapons development.

A day earlier, North Korea made a strong warning of an increasing threat of war, saying the U.S. State Department was making "a final examination" of an attack plan that American forces, with the help of South Korean troops, could carry out within hours of receiving orders.

"The situation on the Korean Peninsula is deteriorating so rapidly that an armed clash may break out quite contrary to the desire of the (North) for the peaceful settlement of the nuclear issue," said a report Tuesday by North Korea's state-run KCNA news agency

The North said it was prepared to answer the threat of an attack with "the unlimited use of means." The United States has 37,000 troops in South Korea.

North Korea has frequently accused the United States of planning an attack, but Tuesday's report was more forcefully worded and more extensive than most recent statements. Washington has said repeatedly that it has no intention of attacking North Korea and wants a diplomatic solution.

The current dispute began in October when U.S. officials said North Korea had admitted having a nuclear weapons program based on uranium enrichment in violation of a 1994 agreement with the United States. Washington suspended oil shipments to North Korea, which then ousted U.N. nuclear inspectors and pulled out of a global nuclear arms control treaty.

While castigating the United States, the North gave elegant treatment to the South Korean delegation. Lim's delegation arrived Monday and was feted at a five-hour banquet. On Tuesday, Lim met with North Korea's No. 2 official, Kim Yong Nam, president of the parliament, as well as Kim Young Sun, a close aide to Kim Jong Il.

South Korean officials said the mission achieved "some degree of success": The delegation conveyed South Korea's anti-nuclear position and heard the North's response.

But the real goal had been a meeting with Kim Jong Il. On Tuesday, South Korean officials had thought chances for a meeting were high. Lim took on the trip a personal letter from his president to the North Korean leader. He passed the letter to Kim through aides, a South Korean Unification Ministry official told local reporters in Seoul on condition of anonymity.

Lim urged high-ranking North Korean officials "not to lose the current opportunity to take visible actions to resolve its nuclear issue but the Northern side repeated its position," the official said.

Lim has met with Kim three times in the past and was instrumental in setting up a North-South summit in June 2000.

South Korean officials also discussed the nuclear issue with Lim Dong Ok, the North's communist party deputy, who oversees Korean unification affairs.

North Korea's barb at the United States fit the pattern of KCNA dispatches in recent weeks that have attacked Washington for its refusal to negotiate with Pyongyang until the North agrees to give up its nuclear program.

Instead, the North is pushing for unconditional, bilateral talks with Washington in hopes of winning a nonaggression treaty and ensuring the survival of its communist regime. The North's Foreign Ministry issued a statement Tuesday through KCNA making the same demand and rejecting any "multilateral talks" — meaning it doesn't want anyone else involved.

Pyongyang is also fiercely opposed to Washington's efforts to shift discussion of the nuclear issue to the U.N. Security Council, which could vote for sanctions against the already impoverished North. North Korea has said it would consider sanctions a declaration of war.