The US government has banned airline passengers from taking all liquids in carry-on bags on non-stop flights to Russia.
The move was announced by Delta Air Lines, the only American carrier with regularly scheduled services to Russia, on its website yesterday.
It comes as Russia today launches the Sochi Winter Olympics, which takes place over the next two weeks, amid security fears.
US officials yesterday warned that terrorists could smuggle explosives into Russia in toothpaste tubes, although it added that there is no specific threat.
The temporary restrictions, which last until the end of the Olympics on February 21, ban carry-on liquids, gels and aerosols on direct flights between the US and Russia.
They exclude prescription medications and do not apply to checked luggage.
Last month, Russia banned all liquids, pastes and gels from its airports and internal flights.