Photo/IllutrationNorth Korean leader Kim Jong Un, center, gives orders on a project to manufacture nuclear weapons. The date is unknown. This photo was distributed by the Korean Central News Agency on Sept. 3, 2017. (Korea News Service)

SEOUL--In preliminary negotiations before their upcoming summit, the United States is demanding that North Korea relocate its nuclear engineers to other countries and discard data from its nuclear development program.

The demands were made in preliminary discussions for the U.S.-North Korea summit scheduled to be held by early June, sources related to North Korea said on May 9.

However, North Korea is resisting the relocation of up to several thousand nuclear engineers and is taking a vague stance on the abandonment of data on its six nuclear experiments and nuclear-related facilities in Yongbyon, they added.

According to the sources, the United States also wants North Korea to abandon all its weapons of mass destruction, including biological and chemical weapons.

In addition, the United States is asserting that it will not allow North Korea to launch a satellite-carrying rocket, which has the same capabilities as long-range ballistic missiles.

Officially, North Korea denies possessing biological or chemical weapons. It is also planning to launch a rocket on a national commemoration day. Therefore, the country is strongly resisting the demands and the assertion.

The difference of opinions has yet to be resolved between the two countries on the “period” and “method” for dismantlement of nuclear bombs and nuclear-related facilities.

The United States wants North Korea to carry out complete, verifiable and irreversible dismantlement in a short period, such as several months or up to two years. However, North Korea prefers to carry it out step by step, spreading the process out over a long period.

As for returns to be made in exchange for dismantlement, the United States is assuming that it will give them after all the measures for dismantlement are complete. But North Korea is seeking to be rewarded each time one of the measures is taken.

Meanwhile, the United States is seeking the relocation of North Korean nuclear engineers and elimination of nuclear development data as part of the “method” for dismantlement.

In the ongoing preliminary negotiations, North Korea has shown a stance that it will accept dismantlement of its nuclear bombs and intercontinental ballistic missiles (ICBM).

However, the United States fears that even if North Korea scraps its nuclear bombs and ICBMs, it can resume nuclear development in the future if it retains its nuclear engineers and data.

North Korean leader Kim Jong Un met again with Chinese President Xi Jinping on May 7 and 8 following their first meeting in late March. Kim made his second visit to China to meet with Xi to weaken the strong U.S. stance by showing close cooperation with China.