The Greek government has asked NATO to consider dispatching a contingent of troops, possibly including U.S. forces, to help provide security at next month's Olympic Games, top Pentagon officials said today.

Defense Secretary Donald H. Rumsfeld and Air Force Gen. Richard B. Myers, chairman of the Joint Chiefs of Staff, said NATO is studying the request at its headquarters in Brussels. They did not provide details of the request and declined to discuss any intelligence indicating that terrorists might be planning to target the Olympics in Athens.

The United States has agreed to contribute 400 special forces troops to help protect the Games, the Associated Press quoted a U.S. counterterrorism official as saying. But it has not yet been decided whether the troops would be in Athens, on the nearby island of Crete or remain on alert in Europe, the news agency reported.

In any case, Rumsfeld and Myers made it clear that any U.S. soldiers helping to provide security for the Games would do so under the auspices of NATO, a 26-nation alliance that includes Greece.

"Greece has been working closely with NATO," Rumsfeld said at a news conference at the Pentagon. "And NATO has been, to the extent it's able, responding to the government of Greece's requests and thoughts and suggestions."

Myers, standing alongside Rumsfeld, said, "The Greek government has made a request of NATO. NATO is evaluating that request. . . . And once that decision's made, then we'll look at the kind of capabilities that might be required to help."

Asked if that help would involve U.S. troops, Myers said, "It's all possible. Sure."

Rumsfeld interjected that "it wouldn't involve U.S. troops, per se. It would be only a NATO mission."

The dispatch of foreign troops or armed guards to Greece for the Olympics is a sensitive issue because the Greek constitution generally prohibits foreigners from bearing arms on Greek soil. There are exceptions, however, for armed guards of foreign leaders and for NATO troops, officials said.

Rumsfeld said Greek authorities "have appropriately addressed [the security issue] from a NATO standpoint, which is permissible from a practical, legal and policy standpoint in their country."

Earlier, Greek officials said they would not allow armed foreign guards to protect athletes at the Olympics and insisted that Greece bears sole responsibility for security at the Games.

Guards accompanying national leaders to the Games would be allowed to carry weapons under existing international protocols, but this is a separate issue from security for the athletes, said George Voulgarakis, Greece's public order minister.

"Leaders, presidents, kings, etc., are one thing, and athletes are another," Voulgarakis said in a statement reported by the Reuters news agency. "Greece is exclusively responsible for the protection and guarding of the athletes."

About 40 foreign leaders, including British Prime Minister Tony Blair and French President Jacques Chirac, are expected to visit Greece during the Games. The official U.S. delegation is to include former president George H.W. Bush and his wife, Barbara, and their twin granddaughters, Jenna and Barbara, the children of President Bush.

In his first press conference in more than a month, Rumsfeld, who has been keeping a relatively low profile lately, expressed optimism about the situation in Iraq despite a persistent insurgency. He pointed to "positive signs," including the strengthening of the Iraqi currency, the opening of a stock market and willingness of thousands of Iraqis to volunteer to serve in the country's various security forces.

Asked about criticism from Sen. John McCain (R-Ariz.), who has said that Rumsfeld was obstinate in not sending more troops to Iraq to carry out the occupation and that his planning for the phase following last year's invasion was "inadequate," Rumsfeld defended his decisions and denied that he was being stubborn.

"I can't imagine what evidence anyone would cite for my obstinacy," Rumsfeld said as reporters burst into laughter. "The fact of the matter is that I have said and have consistently said and repeatedly said, publicly and privately, that the commanders on the ground are the ones that are making the recommendations, and they have recommended the number of troops that were used to win the war very rapidly; they are the ones that have recommended the total number of troops that are there today, and that we have agreed with them. . . . I have not been an advocate of any particular number, nor have I been an opponent of any particular number. I have listened to the arguments of the military commanders, and anyone who suggests to the contrary is mistaken."

As Myers seconded that view, Rumsfeld interjected, "It's a myth. It's an urban myth . . . that's been promoted and passed around, and it's utter nonsense. It's just not true."