Photo/IllutrationU.S. Secretary of State Mike Pompeo, left, and North Korean leader Kim Jong in Pyongyang (From the website of North Korea’s The Rodong Sinmun)

SEOUL--The United States is insisting that North Korea start dismantling its weapons of mass destruction and move them out of the country within six months.

If Pyongyang agrees to the demand, Washington is prepared to remove North Korea from its list of state sponsors of terrorism, according to well-placed sources.

The U.S. demand includes shipping a quantity of North Korea’s nuclear warheads, nuclear materials and intercontinental ballistic missiles overseas within six months, according to the sources.

No overseas destination was publicly given, but the United States or France could be possibilities.

On May 9, North Korean leader Kim Jong Un in a meeting with U.S. Secretary of State Mike Pompeo in Pyongyang sang Donald Trump’s praises by saying he "highly appreciated" the U.S. president's positive attitude toward the summit by suggesting a new alternative proposal.”

He was apparently referring to the U.S. call to start dismantling weapons and missiles in exchange for a delisting of North Korea as a state sponsor of terrorism, the sources said.

But on May 16, North Korea announced that it will indefinitely postpone high-level talks with South Korea and “reconsider” plans for the June 12 meeting between Kim and Trump in Singapore.

By all accounts, Pyongyang and Washington are wheeling and dealing fiercely behind closed doors ahead of the summit, the first between the leaders of the two countries.

North Korea is believed to possess at least 12 nuclear weapons, more than 50 kilograms of weapons-grade plutonium and hundreds of kilograms of highly enriched uranium, along with other nuclear-related material.

U.S. and North Korean officials are expected to discuss how much of the stockpile can be taken out of North Korea within the six-month timetable during working-level talks prior to the summit.

Trump put North Korea back on the list of state sponsors in November, after a nine-year hiatus, allowing the United States to impose more economic sanctions against Pyongyang over its nuclear and missile programs.

The delisting could pave the way for China, Pyongyang’s longstanding ally, and South Korea, to provide humanitarian assistance to North Korea.

Washington and Pyongyang are continuing talks over the method and timing for the dismantling of North Korea’s nuclear arsenal.

In return for the dismantling, North Korea demands that the United States guarantee the safety and survival of the Kim regime as well as a peace treaty.

The United States insists on a “complete,” “verifiable” and “irreversible” dismantling of North Korea’s nuclear program over a short period.

In addition, it also demands that Pyongyang abandon biological and chemical weapons as well and transfer engineers involved in the nuclear program overseas.

The two sides have yet to narrow their differences over these issues, according to the sources.

Trump’s new national security adviser, John Bolton, known for his hard-line stance against North Korea, is pushing for Libya’s model, asserting that North Korea should unilaterally abandon all its nuclear weapons.

Libya shipped nuclear-related equipment and missile launchers to the United States by sea after it announced its decision to abandon nuclear weapons in 2003.