Sochi 2014: US bans carry-on liquids on Russia-bound flights

US authorities announced a temporary ban on Thursday on liquids, gels and aerosols in carry-ons aboard Russia-bound flights, as President Barack Obama said Moscow has an "enormous stake" in thwarting terror at the Winter Olympics.

The Transportation Security Administration directive came a day after Washington warned American and foreign airlines that extremists could hide explosives in toothpaste or cosmetic tubes in an attempt to disrupt the Games, set to start Friday in Sochi. (Also read: Five things to know about Sochi Games)

"I think the Russians have an enormous stake, obviously, in preventing any kind of terrorist act or violence at these venues. They have put a lot of resources into it," Obama told US broadcaster NBC.

"We are consistently working with them to make sure that not only our athletes are safe, but everyone who's attending these Games are safe." (Russia plan glitzy opening ceremony)

Top US diplomat John Kerry urged citizens headed to the Olympics to be vigilant and attentive.

But, he added, "if an American wants to go, including my daughter, I'd say go."

Russia last month banned domestic travelers from having any liquids and gels, including toothpaste, in their carry-ons. (Related: Disgrace that Indians will walk under IOC flag, say ex-Olympians)

Stringent rules on liquids and toothpaste in hand luggage have been standard practice on US carriers after a string of thwarted bomb plots in the years following the September 11, 2001, attacks. But, until now, limited amounts were allowed on board. The banned items, however, can be put in checked baggage, and prescription drugs are allowed.

"As always, our security posture, which at all times includes a number of measures both seen and unseen, will continue to respond and appropriately adapt to protect the American people from an ever evolving threat picture," a Department of Homeland Security official said.

"These measures include intelligence gathering and analysis, deployment of cutting edge technology, random canine team searches at airports, federal air marshals, federal flight deck officers, temporarily restricting certain items and more security measures both visible and invisible to the public." (Olympic Charter quoted as Google Doodle flies gay flag)

In October 1976, Cuban exiles opposed to Fidel Castro's regime brought down a Cubana Airlines flight using plastic explosives hidden in a tube of Colgate toothpaste, killing 78 passengers and crew.

Delta Airlines said on its website that customers traveling between the United States and Russia would have to check in with an airline representative at the airport, not online or using their smartphone or airport kiosks. "Delta encourages customers traveling to and from Russia to arrive at the airport at least two hours in advance of departure time," the airline said. (Who is Shiva Keshavan?)

The chairman of the US House Homeland Security Committee said Americans were not specifically targeted by the toothpaste explosive threat. "The beef they have is really with the Russians," Representative Mike McCaul told CNN. "However, if you blow up an airplane, you will have innocent civilians that could include Americans."

He said the plot originated from the leader of the Chechen rebel extremists, Doku Umarov, who called for attacks on the Games in a video released in July. The Texas Republican also hailed Russian officials for cooperating with the United States on the threat, despite simmering tensions between the former Cold War foes. (India's Sochi Olympics 2014 disgrace: Who said what)

The White House had expressed concern last month about Russia's reluctance to share details of various security threats. Nervousness over possible attacks at the Games, which run until February 23, skyrocketed after two suicide blasts that killed 34 in the southern Russian city of Volgograd in December, blamed on extremists from the Northern Caucasus region.

Russian security forces are fighting insurgents in the area, which is close to Sochi, and militants have threatened to strike targets in Russia during the Olympics. About 40,000 members of the Russian security forces are on duty in and around Sochi, a resort city, in one of the tightest operations ever mounted at an Olympics.

Two US warships are on standby in the Black Sea to offer assistance, including the evacuation of Americans in the event of an attack.