WASHINGTON Russia is not cooperating enough in sharing intelligence with the United States about possible threats by militants to attack participants at the Winter Olympics in Sochi, U.S. security officials say.
"I'd say that Russia has not been forthcoming in sharing specific threat information," said a senior U.S. official.
A second U.S. official said the United States believes Russia has established effective "ironclad" security measures in and around Sochi, but affirmed that Washington is concerned about Moscow's reluctance to share threat information.
After two suicide bombings killed 34 people in the southern city of Volgograd last month, Russia has been keen to assure athletes and spectators that the Olympics in Sochi, in the turbulent North Caucasus region, will be safe.
Islamist militants in the North Caucasus have threatened to attack the Games.
A U.S. official said that given the formidable security in Sochi, the most likely targets for attacks are other places, including Moscow.
Would-be attackers "don't have to hit the hard targets. They just have to hit the soft target to be effective," the official said.
The U.S. officials did not give details of possible threats. Their expression of concern came despite a phone conversation on Tuesday between Putin and President Barack Obama, during which security in Sochi was discussed.
White House press secretary Jay Carney said the United States had "offered its full support, and any assistance to the Russian government in its security preparations for the Sochi games." He added that FBI and U.S. diplomatic security personnel would be sent to Sochi to work with Russian authorities.
The United States is offering American technology used to thwart roadside bombs in places like Afghanistan to bolster Russia's security during the Olympics and the U.S. military is making two ships deployed in the Black Sea available if needed during the Games.
Pentagon spokesman Rear Admiral John Kirby said the U.S. military was conducting "prudent" planning in case any American assets might be required during the Games. But he added that security was up to Russia, which so far had made no requests for U.S. assistance.
"The United States has made clear very early on (to Russia) that we're willing to assist in any way that we can. There's been no request for such assistance," Kirby told a news conference.
Kirby stressed that Russia had not asked for any U.S. counter-bomb equipment and that such discussions were informal. He also played down the idea the Pentagon is actively planning for the potential evacuation of U.S. citizens from Sochi.
"There's been no specific planning for evacuation. There's been no request to have a plan to do that right now," he said.
Kirby said he thought the Russians were taking security "very, very seriously."
"And I believe they are applying as much energy as possible to providing security for the Games," he said.
Dmitry Peskov, Putin's chief spokesman, affirmed Russia's view that decisions about how to safeguard the Olympics are the host country's responsibility.
"Threats exist for Olympics held in any location, and each country takes measures to provide security," Peskov said. Russia's interior ministry and FSB intelligence service declined immediate comment.
Laith Alkhouri, who monitors extremist websites for Flashpoint Partners, a firm which consults on counter-terrorism issues for U.S. government agencies and private businesses, said one of the latest threats to surface was issued by Ansar al-Sunnah, a militant group in Dagestan, threatening a possible attack with chemical weapons.
"In case you do not...withdraw your armies from the land of the Caucasus...the attacks will continue and they will elevate to chemical attacks," the group said in a message posted on what Alkhouri characterized as an "official" militant website. "The source of the message is no doubt authentic," Alkhouri said.
A U.S. security official said the U.S. believed the likelihood of Sochi related attacks with real chemical weapons, such as the poison gas shells which the Syrian government allegedly used last year, was "pretty low", although in the past militants in Iraq had hijacked and blown up trucks carrying chlorine gas.
(Additional reporting by Steve Gutterman in Moscow and Steve Holland and Phi Stewart in Washington; editing by Gunna Dickson)