Russia on Wednesday accused the United States of "crude and clumsy" spying on its territory after a suspected CIA agent was caught in Moscow seeking to recruit an agent while disguised in a blonde wig.

The foreign ministry issued an official protest to the U.S. ambassador who it summoned to an early morning meeting, but signs also grew that neither side wanted the Cold War-style incident to develop into a full scale crisis.

Japan's Prime Minister Shinzo Abe said Wednesday he may meet North Korean leader Kim Jong-Un if it could help resolve the long-pending issue of Pyongyang's kidnapping of Japanese citizens.

"If a summit meeting is deemed as an important means in considering ways to resolve the abduction issue, we must take it into consideration as a matter of course in negotiating with them," Abe told a parliamentary committee.

Russian Foreign Minister Sergei Lavrov on Wednesday called on the Syrian opposition to support Moscow and Washington in their efforts to work towards convening a peace conference to end the bloodshed in Syria.

"It is important for all participants to express articulate support for the Russian-US initiative to implement the Geneva communique," Lavrov was quoted as saying in the Swedish town of Kiruna by Russian news agencies.

North Korea has yet to develop a nuclear warhead small enough to fit on a missile, a senior U.S. official said on Wednesday, contradicting a recent U.S. military intelligence report.

The North claimed its third atomic test staged in February involved a "miniaturized and lighter" warhead, prompting speculation that it had acquired the crucial technology to fit nuclear devices to a missile delivery system.

The leak which prompted the seizure of journalist phone records at a U.S. news agency was a "very serious" matter which "puts the American people at risk," Attorney General Eric Holder said Tuesday.

Responding to fierce criticism of a violation of news media rights, Holder said, "I've been a prosecutor since 1976. And I have to say that this is among, if not the most serious... leaks I've ever seen."

A U.S. consulate in China has suspended some of its operations, an official said Tuesday, after receiving an envelope which contained an "unidentified substance", reportedly white powder.

The consulate in the southern city of Guangzhou "received an envelope which contained an unidentified substance," on Monday, deputy U.S. embassy spokesman Justin Higgins told Agence France Presse, adding that no one had been injured.

Syria wants more details of a Russian and U.S. proposal for a peace conference before deciding whether to attend, Information Minister Omran al-Zohbi has said.

Interviewed late Tuesday by the Lebanese Al-Manar television, Zohbi also insisted that Syrian President Bashar Assad's future would be decided at the ballot box.

Russia on Tuesday ordered the expulsion of an alleged American CIA agent working undercover at the U.S. embassy who was discovered with a large stash of money trying to recruit a Russian agent.

Russia's Federal Security Service (FSB, ex-KGB) identified the man as Ryan C. Fogle -- third secretary of the political section of Washington's embassy in Moscow -- and said he had been handed back to the embassy after his detention.

U.S. envoy on North Korea, Glyn Davies, said Friday that Pyongyang should expect no reward for its apparent decision to cancel an expected missile launch at a time of elevated military tensions.

"I don't think we should any longer be in the business of treating the absence of bad behavior as something that needs to be rewarded," Davies told reporters after a meeting in Seoul with his South Korean counterpart Lim Sung-Nam.

Kuwait's government boycotted a parliament session on Tuesday after MPs filed requests to grill the oil and interior ministers over alleged violations, including a $2.2 billion penalty payment to U.S. Dow Chemical.

"Due to the absence of cabinet ministers and as I was informed the government will not attend, I adjourn the parliament session until Wednesday," speaker Ali al-Rashed told those MPs present in the chamber.