Washington - The White House stopped short of expressing full confidence in Russia's Olympics security operation on Wednesday following a call between presidents Barack Obama and Vladimir Putin.
The leaders discussed how to ensure next month's Winter Games in the Black Sea resort of Sochi are “safe and secure”, as well as US offers of security assistance, in a call on Tuesday.
At a White House briefing, spokesman Jay Carney said that there was “concern” in Washington about an uptick in threat reporting from Islamic extremists relating to the Sochi Games.
He said the United States would send diplomatic security and FBI agents who would liaise with Russia security to protect American athletes and spectators.
But he did not take several opportunities offered by journalists to express full confidence in Russia's preparations, amid growing concern in Washington - and claims by some lawmakers - that Moscow is not taking advantage of US offers of assistance.
Asked to take stock of Russia's security posture ahead of the Games, Carney said : “I wouldn't be qualified or wouldn't want to venture to assess overall.”
“These kinds of major events around the world obviously present security challenges,” he said, without saying whether Russia had accepted US offers of help.
“The president spoke with President Putin about this. We have offered any assistance that they might want to avail themselves of.”
The call came amid signs of subtle but rising pressure on Russia over securing the Games from Washington.
On Monday, the Pentagon said it was ready to deploy air and naval assets - including two ships - to help secure the Olympics, which begin on February 7.
US Defence Secretary Chuck Hagel had already offered American support during a January 4 phone call with his Russian counterpart Sergei Shoigu.
Islamist insurgents based in North Caucasus republics such as Dagestan who are seeking their own independent state have vowed to disrupt the Sochi Games in an effort to undermine Putin.
In a video threat posted on a prominent North Caucasus Islamist website, two men sitting in front of a jihadist flag warn of planned attacks at the event.
The introduction says the men went on to commit two suicide bombings in the southern city of Volgograd last month - Russia's deadliest in three years - which killed a total of 34 people.
Earlier this month, the State Department warned that Americans headed to Sochi should be vigilant to ensure their security.
On Sunday, several prominent US lawmakers raised new concerns about Russia's security efforts to protect the Games, despite Moscow's effort to encircle the host city in a ring of steel.
Michael McCaul, chairman of the House homeland security committee, said there had been good co-operation between Russian authorities and the Federal Bureau of Investigation (FBI).
But he told ABC News in an interview from Moscow: “It could be a lot better.”
Another Republican lawmaker, House intelligence committee chairman Mike Rogers, said US officials were not getting all the information they needed to protect athletes at the Games.
“What we're finding is they aren't giving us the full story about what are the threat streams, who do we need to worry about,” he said.