Photo/IllutrationNorth Korean leader Kim Jong Un, second from right, gives instructions on a project to manufacture nuclear weapons. This photo was distributed by the Korean Central News Agency on Sept. 3, 2017. (Korea News Service)

SEOUL--North Korea intends to comply with the complete dismantlement of its nuclear weapons program as sought by the United States, according to sources familiar with U.S.-North Korea relations.

The intent was shown in preliminary talks for the summit between the leaders of the two countries, which is expected to be held by early June, they said.

In addition, North Korea plans to accept inspections of its nuclear weapons for the first time and also the dismantlement of intercontinental ballistic missiles (ICBMs), they said.

However, a difference of opinion remains on the timetable for complying with the complete dismantlement and what benefits North Korea will receive in return for acquiescing to this and other demands, they added.

According to the sources, a total of three U.S. CIA officials or nuclear experts visited North Korea for about a week from late April.

In their talks with North Korean officials, it became likely that the two countries will agree in their summit on the complete dismantlement of nuclear weapons, inspection of nuclear weapons and dismantlement of ICBMs.

In the historic April 27 summit between South Korea and North Korea, North Korean leader Kim Jong Un also showed a stance that his country will accept denuclearization measures in complete, verifiable and irreversible methods as sought by the United States.

The United States has already started talks with the International Atomic Energy Agency (IAEA) so that the organization will play the central role in implementing the denuclearization measures. The United States will also ask Japan for cooperation.

In the six-nation talks held in the 2000s, North Korea disclosed its nuclear-related facilities, including reactors, and production volume of weapons-grade plutonium.

However, North Korea refused to accept verification measures, including inspections that used scientific methods. As a result, dismantlement of nuclear weapons was not achieved.

As for nuclear weapons, North Korea has refused to disclose them, saying that they are military secrets.

In the ongoing preliminary talks, however, the country showed a stance that it will accept inspections of all its nuclear-related facilities and nuclear weapons.

Regarding the period until dismantlement, the United States is telling North Korea that it wants to achieve denuclearization in a short time.

That means that the United States hopes to complete the process from disclosure of the weapons and facilities to their dismantling by early 2021, which is the end of the Trump administration’s term.

On the other hand, North Korea is requesting that the United States guarantee the continuation of the current Kim-led regime, normalize diplomatic relations between the two countries and remove economic sanctions.

North Korea is telling the United States that it wants to receive those benefits each time it takes a step to denuclearize.

As for missiles, if the United States and North Korea agree to dismantle only ICBMs, Japan will remain in range of North Korea’s mid- and short-range ballistic missiles.

With the threat from those missiles in mind, South Korea agreed with North Korea in their April 27 summit meeting that both countries will completely halt all their hostile acts toward one another.

Japan could face a challenge of how it will deter the North Korean missile threat.

Meanwhile, many hurdles remain for the complete dismantlement of nuclear weapons and nuclear-related facilities. North Korea’s nuclear development program is shrouded in secrecy. Therefore, it is difficult for inspections to verify if the country is following through on its declaration.

Several years ago, Japan, the United States and South Korea estimated that North Korea possessed at least 12 nuclear weapons. However, the figure is believed to have increased since then.

According to South Korea’s National Defense Ministry and other sources, North Korea has produced at least 50 kilograms of weapons-grade plutonium. Each nuclear weapon is said to require four to six kilograms of plutonium.

However, nuclear reactors that produce plutonium are large. Therefore, they can be monitored to some degree by satellites.

On the other hand, the actual state of nuclear development that utilizes highly enriched uranium is virtually unknown.

North Korea is believed to have a capability of producing about 80 kilograms of highly enriched uranium a year. The volume corresponds to the manufacture of three nuclear bombs.

Centrifugal machines necessary for uranium enrichment are small and can be housed in underground facilities. Therefore, the actual conditions of operations of those machines are unclear.

The number of underground facilities in North Korea is estimated to be in the several thousands. Even if the United States or the IAEA are allowed to inspect them freely, it is difficult to grasp the entire picture of nuclear weapons and uranium enrichment facilities unless North Korea gives its full cooperation.