The United States plans to send a top diplomat to North Korea next week in response to the communist country's recent moves to restart a nuclear facility in the face of U.S. opposition.

Christopher Hill, the chief U.S. negotiator in the six-party talks over North Korea's nuclear program, is preparing to leave Monday for South Korea and then its neighbor to the north.

Tensions between the United States and North Korea have been rising since reports surfaced that the country was reassembling nuclear processing facilities at Yongbyon that had been demolished last year in accordance with an agreement between the countries.

The demolition was among the conditions for the United States taking North Korea off its list of terror-supporting countries, and U.S. officials have suggested that North Korea's reversal is a form of protest at delays on the diplomatic front.

On Wednesday, the chief inspector in North Korea for the International Atomic Energy Agency, IAEA, announced that the country has removed the inspection seals and all surveillance equipment from the nuclear reprocessing facility at Yongbyon.

U.N. inspectors have been ordered to leave, and U.S. officials and IAEA representatives confirmed that reprocessing at the facility could begin in a matter of days.

Secretary of State Condoleezza Rice responded then that the moves would "only deepen its isolation."

She then insisted the six-party talks with the North Koreans to disarm are not dead.

Yongbyon has 3 parts to it: the nuclear reactor, the cooling ponds for the spent fuel rods and the reprocessing plant. The reprocessing plant is the easiest to restart. Earlier this year the North Koreans blew up the cooling tower, a largely symbolic act, according to experts. Plutonium can still be extracted from the spent fuel for use in a bomb without the cooling facility.

The North Koreans had completed approximately 8 of 11 requirements to denuclearize in exchange for aid but talks with the U.S., China and others hit a snag when the U.S. demanded greater verification and soil samples from the facility and refused to take North Korea off the U.S. State Department’s terror list, which essentially blocked the Koreans from receiving trade money.

North Korean leader Kim Jong Il reportedly suffered a stroke in August and it isn't clear how much control he has over his country.

FOX News' Jennifer Griffin and Nina Donaghy and The Associated Press contributed to this report.