Washington ? The Bush administration pressed North Korea diplomatically Monday to refrain from restarting a dormant nuclear reactor, even as Defense Secretary Donald H. Rumsfeld warned that the U.S. military could simultaneously take on both Iraq and the communist Pyongyang regime.

“We are capable of fighting two major regional conflicts,” Rumsfeld said at the Pentagon. “We’re capable of winning decisively in one and swiftly defeating in the case of the other, and let there be no doubt about it.”

Rumsfeld stressed that no military action to halt Pyongyang’s renewed nuclear ambitions was imminent, and White House officials said the United States intended to pursue a diplomatic course to persuade North Korea to abandon efforts to expand its nuclear arsenal. Discussions on this matter are ongoing with China, Russia and other countries, the State Department said.

The Bush administration also renewed calls for Pyongyang to restore U.N. surveillance gear that it dismantled at a nuclear reactor at Yongbyon and refrain from restarting the facility. The reactor was a key site in North Korea’s past efforts to produce nuclear weapons, U.S. officials say.

Moving to restart the reactor will only deepen North Korea’s isolation, senior Bush administration officials said.

North Korea has said it needs the power the reactor would produce, but Joint Chiefs of Staff Chairman Gen. Richard Myers said the reactor would provide negligible energy to the country’s grid. Instead, U.S. officials accuse Pyongyang of planning to restart the facility to support weapons programs.

The Vienna-based International Atomic Energy Agency, a U.N. monitoring agency, said Pyongyang this weekend unsealed a storage chamber at Yongbyon holding 8,000 irradiated fuel rods. Plutonium in the rods could yield four or five nuclear weapons within months, experts say.

A senior administration official said the United States did not believe the North Koreans had opened the canisters containing the fuel rods.

North Korea said Monday the “nuclear issue” could be settled if Washington signed a nonaggression treaty with it.

But the Bush administration, burned by North Korea’s recent acknowledgment that it continued its nuclear efforts despite a 1994 agreement not to do so, sees little reason to negotiate.

“We will not give in to blackmail,” State Department spokesman Philip Reeker said. “The international community will not enter into dialogue in response to threats or broken commitments. And we’re not going to bargain or offer inducements for North Korea to live up to the treaties and agreements that it has signed.”

Rep. Curt Weldon, R-Pa., a senior Armed Services Committee member, said he was seeking visas to lead a congressional delegation to Pyongyang for talks with North Korean officials.

“When you don’t have dialogue, that is when the problems develop and that’s my concern with North Korea,” Weldon said.

Asked whether the U.S. military has drawn up plans to make war on North Korea, Rumsfeld said, “One of the assignments of the department is to prepare for a whole host of contingencies. We tend not to get into details as to what those contingencies might be.”

The Clinton administration considered bombing the Yongbyon site in 1994 before North Korea agreed to shut it down. Under the 1994 agreement, North Korea pledged to freeze and eventually dismantle its nuclear weapons program in exchange for international aid to build two power-producing nuclear reactors.

“The situation today is somewhat different from then,” Rumsfeld said, without elaborating.

U.S. intelligence officials believe North Korea made one or two nuclear weapons in the 1990s with plutonium, and they fear a larger North Korean arsenal. They also are concerned that Pyongyang could provide nuclear materials and know-how to other unfriendly nations.

Nuclear weapons can also be made with enriched uranium, and U.S. officials say North Korea is stepping up efforts to enrich uranium to make more weapons. On Oct. 4, North Korea acknowledged the enrichment program to American diplomats, setting off a crisis.

In response, President Bush halted oil shipments the United States has provided the energy-poor country. The North Koreans then said they would restart nuclear energy facilities shut down as part of the 1994 pact.