(CNN) -- North Korea has asked U.N. nuclear agency inspectors "to remove seals and surveillance equipment to enable them to carry out tests" at the Yongbyon reprocessing plant, the agency's director-general said.
A South Korean looks at the demolition of a cooling tower at the North's Yongbyon nuclear complex, June 27, 2008.
But Mohamed ElBaradei, director-general of the International Atomic Energy Agency, said Monday that the North Koreans said this will "not involve nuclear material." The news comes amid fears that North Korea may want to resume its nuclear program.
ElBaradei said the agency has "continued to verify the shutdown of the nuclear facilities at Yongbyon and to implement the ad hoc monitoring and verification arrangement, with the cooperation of the Democratic People's Republic of Korea."
While not asked to take part in "disablement activities," the agency has observed and documented them.
He said agency inspectors have observed that "some equipment previously removed by the DPRK during the disablement process has been brought back. This has not changed the shutdown status of the nuclear facilities at Yongbyon.
"This morning, the DPRK authorities asked the agency's inspectors to remove seals and surveillance equipment to enable them to carry out tests at the reprocessing plant, which they say will not involve nuclear material."
He said he is hopeful that conditions can be developed for North Korea "to return to the Non-Proliferation Treaty at the earliest possible date and for the resumption by the agency of comprehensive safeguards."
Last week, a South Korean news agency reported that North Korea is restoring a reactor at the Yongbyon nuclear complex and no longer wants to be removed from a U.S. list of countries that sponsor terrorism.
Hyun Hak-Bong, a chief North Korean negotiator at six-nation talks, told reporters that his country is "thoroughly preparing to restart" the reactor and that reporters would "know soon" when his country would do that, the Yonhap news agency said.
But a senior U.S. diplomat said the announcement could simply be a bargaining ploy in the long-running negotiations aimed at halting North Korea's nuclear program.
The United States had seen no indications North Korea is actually rebuilding its reactor, the diplomat said.
Diplomats have said some of the disabled parts have been moved around from storage since the latest impasse in the negotiations began, but the American diplomat believes that is a negotiating tactic.
The U.S. envoy to North Korea addressed the fresh standoff with reporters Monday, saying the United States is still trying to strike a deal with Pyongyang to come clean on its nuclear claims.
"The six-party process has had its difficult moments and we are certainly experiencing one now," Assistant Secretary of State Chris Hill told reporters.
Although North Korea has threatened to restart its nuclear reactor at Yongbyon, "We don't expect any dramatic developments in the next few days," he said.
Hill said U.S. officials have the impression North Korea wants to reach agreement with Bush administration before it leaves office. However, "North Korea is not a country that is given to opening itself up," he added.
Earlier, a senior State Department official told CNN that in recent weeks, the North Koreans have taken a "harder-line stance toward the six-party talks." The official said the request for removal of the seals is part of that process.
But there is one aspect the U.S. is unsure about, the official said: "What remains to be determined is the relationship of this new and tougher approach to the health of Mr. Kim."
U.S. intelligence officials told CNN last week that North Korean leader Kim Jong Il has been suffering serious health problems, and may have had a stroke.
The official said the United States is working with its allies to figure out the next move.
North Korea had agreed to disable the Yongbyon nuclear complex by October in exchange for a pledge from the United States to lift some sanctions and remove North Korea from a list of countries that sponsor terrorism.
In June, North Korea declared in a 60-page document that since 1986, it had produced enough plutonium for seven nuclear bombs. Soon after its declaration, the North publicly destroyed a cooling tower at the Yongbyon complex.
Progress has stalled since then.
North Korea has said it stopped disabling the Yongbyon complex August 14. It also said it would consider rebuilding the reactor because the United States had not removed it from the list of countries that sponsor terrorism.
A U.S. State Department spokesman, Robert Wood, said then that the North would be taking "a step backward" if it rebuilt the reactor.
On September 3, North Korea started to reassemble parts of the complex, the Yonhap news agency reported, citing diplomatic sources.
A spokesman for the U.S. National Security Council, Gordon Johndroe, said then that "the process is not moving in the direction we want to move in.
"We think North Korea is taking these steps because it has not been removed from the terrorism list," he said.
One sticking point between the United States and North Korea involves verification.
Washington has said it will not remove North Korea from the terrorism list until North Korea agrees to set up an internationally recognizable mechanism to verify its declaration.
The United States has demanded that inspectors be given the right to visit all suspected nuclear facilities without notice, but North Korea rejects that provision.