Russia says it has had no involvement in the travel plans of fugitive US intelligence leaker Edward Snowden.
His whereabouts are unclear after he flew from Hong Kong to Moscow on Sunday. His passport has been revoked.
Foreign Minister Sergei Lavrov insisted Mr Snowden had not crossed the border and rejected what he termed US attempts to blame Russia for his disappearance.
US Secretary of State John Kerry said the US did not seek "confrontation" but Russia should hand over Mr Snowden.
Correspondents say Mr Lavrov's comments suggest that Mr Snowden remained air-side after landing at Moscow's Sheremetyevo airport, and so has technically never entered Russian territory.
"We are in no way involved with either Mr Snowden, his relations with US justice, nor to his movements around the world," Mr Lavrov said.
"He chose his itinerary on his own. We learnt about it... from the media. He has not crossed the Russian border.
"We consider the attempts to accuse the Russian side of violating US laws, and practically of involvement in a plot, to be absolutely groundless and unacceptable."
The 30-year-old IT expert is wanted by the US for revealing to the media details of a secret government surveillance programme, which he obtained while working as a contractor for the National Security Agency (NSA).
Speaking during a visit to Saudi Arabia, Mr Kerry said the transfer of Mr Snowden was a matter of rule of law, and that Russia should remain "calm".
He is charged with theft of government property, unauthorised communication of national defence information and wilful communication of classified communications intelligence.
Mr Snowden has applied for asylum in Ecuador. The US has revoked his passport.
Reuters news agency quotes a Moscow airport source as saying that Mr Snowden arrived in Moscow from Hong Kong on Sunday afternoon and was due to depart for the Cuban capital, Havana, the following day, but did not use the ticket.
The source said he was travelling with Sarah Harrison, a British legal researcher working for the anti-secrecy group Wikileaks.
Meanwhile, China has also described US accusations that it facilitated the departure of fugitive Edward Snowden from Hong Kong as "groundless and unacceptable".
A foreign ministry spokeswoman said the Hong Kong government had handled the former US intelligence officer's case in accordance with the law.
The White House had criticised what it termed "a deliberate choice to release a fugitive despite a valid arrest warrant".
The Chinese government has expressed deep concern about Mr Snowden's allegations that the US had hacked into networks in China.
Tuesday saw the official newspaper of the Chinese Communist Party praise Mr Snowden for "tearing off Washington's sanctimonious mask".
In a strongly worded front-page commentary, the overseas edition of the People's Daily said: "Not only did the US authorities not give us an explanation and apology, it instead expressed dissatisfaction at the Hong Kong Special Administrative Region for handling things in accordance with law.
"In a sense, the United States has gone from a 'model of human rights' to 'an eavesdropper on personal privacy', the 'manipulator' of the centralised power over the international internet, and the mad 'invader' of other countries' networks."
Speaking during a visit to India, US Secretary of State John Kerry said it would be "deeply troubling" if it became clear that China had "wilfully" allowed him to fly out of Hong Kong.
"There would be without any question some effect and impact on the relationship and consequences," he said.
He also called on Russia to "live by the standards of the law because that's in the interests of everybody".
Mr Snowden was in hiding in Hong Kong when his leaks were first published.
He is being supported by the whistleblowing website Wikileaks, which said on Sunday that he was heading to Ecuador accompanied by some of its diplomats and legal advisers.
Ecuador is already giving political asylum at its London embassy to Wikileaks founder Julian Assange, who is wanted for questioning in Sweden over allegations of sexual assault - which he denies.
Mr Snowden's leaks have led to revelations that the US is systematically seizing vast amounts of phone and web data under an NSA programme known as Prism.
US officials have defended the practice of gathering telephone and internet data from private users around the world.
They say Prism cannot be used to target intentionally any Americans or anyone in the US, and stress that it is supervised by judges.
20 May: Snowden flies from Hawaii to Hong Kong.
5 June: From Hong Kong, Snowden discloses details of what he describes as a vast US phone and internet surveillance programme to the UK's Guardian newspaper.
23 June: Snowden leaves Hong Kong on a flight to Moscow. He is currently thought to remain airside at Sheremetyevo airport.
From Moscow, Snowden could fly to Cuba, en route to Ecuador, which has said it is "analysing" whether to grant him asylum.
Venezuela had also been considered a possible destination for Snowden, however it is thought he would only pass through on his way to Ecuador.
Snowden is reported to have requested asylum in Ecuador, which previously granted haven to Wikileaks founder Julian Assange in its London embassy.