China said publicly Thursday it was deeply concerned over a possible long-range missile launch by North Korea, while Russia summoned Pyongyang's ambassador in Moscow to express its alarm.

The moves by the communist state's last two major allies followed similar actions by the United States and Japan. A Pentagon official reiterated Thursday the North risked unspecified retaliation if it went ahead with the launch.

China is "very concerned about the current situation," the Foreign Ministry in Beijing said.

The Russian Foreign Ministry said it warned Ambassador Pak Ui Chun against anything that could destabilize the region or "complicate the search for a settlement to the Korean Peninsula's nuclear problem."

Worries have grown in recent weeks after reports of activity at the North's launch site on its northeastern coast, where U.S. officials say a Taepodong-2 missile — believed capable of reaching the United States — is possibly being fueled. Pyongyang also asserted this week its right to launch a satellite, which it claimed to have done after its last long-range missile launch in August 1998.

"If such a launch takes place, we would seek to impose some cost on North Korea," Peter Rodman, an U.S. assistant secretary of defense, said Thursday.

Vice President Dick Cheney said North Korea's missile capabilities "are fairly rudimentary" and expressed skepticism the missile could reach U.S. territory. He rebuffed suggestions that Washington launch a pre-emptive strike.

"I think that at this stage we are addressing the issue in a proper fashion," Cheney told CNN. "And I think, obviously, if you're going to launch strikes at another nation, you'd better be prepared to not just fire one shot."

South Korea's Defense Minister Yoon Kwang-ung said Thursday "it is our judgment that a launch is not imminent."

Seoul — wary of tensions that could roil its economy — has sought to downplay concerns over a possible launch. South Korea has sat in the crosshairs of hundreds of North Korean missiles and artillery for years, remaining technically at war with Pyongyang.

If the North fires a missile toward the South, combined U.S. and South Korean forces will be "ready to intercept it immediately," Yoon told a parliamentary meeting.

But U.S. National Security Adviser Stephen Hadley, briefing reporters during a visit by President Bush to Hungary, expressed reservations that the United States could intercept and destroy such a missile, saying the U.S. missile defense system was still in a developmental stage.

Hadley also said Pyongyang's "preparations are very far along" for a launch. "What we hope they will do is give it up and not launch."

Foreign policy analyst John Swenson-Wright, in an e-mail to The Associated Press, said the likely inability of the United States to intercept a missile launch was the reason Washington wants to see the crisis defused through diplomacy — "while at the same time maintaining a tough, uncompromising position in public."

Swenson-Wright, of the British think tank Chatham House, also said the danger was that Pyongyang might underestimate Washington's intentions, based on inconsistent past signals from the White House.

"Pyongyang may judge that it can get away with a launch without experiencing immediate and costly retaliation — whether economic, political or military — and it may believe that the legal ambiguity surrounding its missile program gives it a legitimate basis to launch," he said.

A North Korean diplomat reportedly said Wednesday that his country wants talks with Washington over the issue, but John Bolton, U.S. envoy to the United Nations, repeated the U.S. rejection of that idea Thursday.

"You don't initiate talks by threatening to launch an ICBM," or intercontinental ballistic missile, Bolton said.

Instead, Washington wants Pyongyang to resume six-nation nuclear talks, which also include China, Japan, Russia and South Korea. The North has boycotted talks since November, angered by a U.S. crackdown on its alleged illicit financial activity.

China also urged a return to talks.

Bolton said the United States is "very encouraged" at China and Russia's strong concern over a possible missile test.

"I think we have again shown there is complete international unanimity that the North Koreans should not undertake this launch," Bolton said. "We'll keep working on it, but I think we've shown there's simply no support for this threatening gesture the North has made."

The North agreed at the round of talks in September to abandon its nuclear program in exchange for security guarantees and aid, but no progress has been made on implementing the accord.

Pyongyang has complained in recent weeks about alleged American spy flights, including over the missile test site. On Thursday, the North admonished Washington again.

"The U.S. imperialist warmongers have been intensifying military provocations against" the North, the official Korean Central News Agency said. "The ceaseless illegal intrusion of the planes has created a grave danger of military conflict in the air above the region."

Washington has sent ships near the Korean coast capable of detecting and tracking a missile launch, a Pentagon official said Wednesday.

Also, South Korean aircraft have been flying reconnaissance over waters between the Korean Peninsula and Japan, the official said on condition of anonymity because he was unauthorized to speak on the subject. Tokyo, too, has sent ships and planes to monitor North Korea, officials said.

The North claims to have a nuclear weapon but is not thought to have an advanced design that could be placed on a warhead.