WASHINGTON (CNN) -- North Korea has stepped up disablement of its nuclear reactor and allowed surveillance at its nuclear facility to resume, the U.S. State Department said Friday.
North Koreans have allowed the resumption of surveillance of its nuclear sites.
Pyongyang has put back all seals on equipment at the facility and reinstalled surveillance equipment, said State Department spokesman Sean McCormack.
He added that U.S. monitors at the site reported North Korea also removed 60 percent of the spent fuel rods at the reactor.
"On the reactor, they have actually gone beyond where they were prior to their reversing the disablement steps," McCormack said.
He noted that North Korea has made some progress in other related areas but still has not reversed all of the gains it made in recent weeks.
Earlier this week North Korea resumed the process of dismantling its nuclear reactor, once again granting the U.N. nuclear watchdog, the International Atomic Energy Agency, access to its nuclear facility at Yongbyon.
The moved came only days after the United States removed North Korea from its list of states that sponsor terrorism.
North Korea halted the disabling of the plutonium-producing plants in August after a stalemate over verification measures. Washington had said it would not take North Korea off the state terrorism list until Pyongyang agreed to set up an internationally recognizable mechanism to verify it was revealing all its nuclear secrets.
North Korea rejected that provision and, on October 9, said nuclear inspectors were no longer welcome at its facilities.
On Saturday, the United States removed North Korea from the list of terrorism sponsors after it said the two countries reached agreement on a number of verification measures.
These include having participation by all members of the six-party talks, settling on the role of the U.N. nuclear watchdog agency, providing access to all of North Korea's nuclear facilities and deciding what procedures would be used in the verification process.
McCormack said envoys from the participants in the six-party talks -- the United States, North Korea, South Korea, China, Japan and Russia -- will meet shortly to sign the verification agreement reached between North Korea and the United States.
Kim Sook -- South Korea's chief envoy to the international disarmament talks with North Korea -- said the move by the United States "completely reverses" the communist nation's decision to halt its disabling process.
North Korea agreed to abandon its nuclear weapons program on a promise that it would receive energy aid equivalent to a million tons of heavy fuel oil from the nations involved in the disarmament talks.
In June, North Korean officials turned over to China a 60-page declaration, written in English, that details several rounds of plutonium production at the Yongbyon plant dating back to 1986.
In it, North Korea acknowledged producing roughly 40 kilograms of enriched plutonium -- enough for about seven nuclear bombs, according to the U.S. State Department.
Soon after, North Korea publicly destroyed a water cooling tower at the Yongbyon facility. At the time, the country said it would completely dismantle its Yongbyon nuclear complex by October.