Story highlights Seoul says the North's demands are "preposterous"

The North lists "practical measures" it says the U.S. and South Korea should take

It wants U.N. sanctions to be lifted and no more U.S.-South Korean military drills

The U.S. has said talks can only happen if the North moves away from its nuclear program

North Korea on Thursday set out demanding conditions for any talks with Washington and Seoul, calling for the withdrawal of U.N. sanctions against it and a permanent end to joint U.S.-South Korean military exercises.

The United States and South Korea "should immediately stop all their provocative acts against the DPRK and apologize for all of them," the North's National Defense Commission said in a statement carried by state-run media, using the shortened version of North Korea's official name, the Democratic People's Republic of Korea.

The commission listed a number of "practical measures" it said the United States and South Korea should take if they want to avoid "sledge-hammer retaliatory blows of the army and people" of North Korea and if "they truly stand for dialogue and negotiations."

But the nature of the demands, such as the lifting of the U.N. sanctions imposed after the North's latest nuclear test, appeared to offer almost no chance of negotiations between the two sides amid heightened tensions on the Korean Peninsula.

"It is hard to understand North Korea's claims," Cho Tai-young, a spokesman for the South Korean foreign ministry, said at a news briefing. "They are preposterous."

A torrent of unnerving threats from Pyongyang in recent weeks has strained already fragile relations in the region. The North's rhetoric intensified when the U.N. Security Council voted last month to slap the tougher sanctions on the regime and amid the U.S.-South Korean military drills under way in South Korea at the moment.

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The United States said this month that for it to enter talks, North Korea would have to show a serious commitment to moving away from its nuclear program, something the regime of Kim Jong Un insists it won't do.

On Thursday, the North suggested that the United States would have to make the first move on the nuclear issue.

"They should bear in mind that the denuclearization of the Korean Peninsula can begin with the pullout of the nuclear war means introduced by the U.S. and this may lead to the global denuclearization," the defense commission said.

North Korea has repeatedly described the annual military exercises taking place in South Korea as threats of nuclear war, singling out aspects of the drills like the practice mission flown by U.S. stealth bombers as evidence. The stealth bombers can carry conventional or nuclear weapons, but they used inert munitions in their training flight.

The United States says such displays of military strength during the drills were aimed at reassuring it allies in the region, not antagonizing the regime in Pyongyang.

President Barack Obama warned Kim Jong Un this week that the North's threats against the United States and South Korea had only served to isolate the regime further.

"This is the same kind of pattern that we saw his father engage in and his grandfather before that," Obama said in an interview with NBC News broadcast Tuesday, referring to the two previous North Korean leaders Kim Jong Il and Kim Il Sung.

"Since I came into office, the one thing I was clear about was, we're not going to reward this kind of provocative behavior. You don't get to bang your spoon on the table and somehow you get your way," he said.