The U.S. military said on Monday that air and naval assets, including two ships in the Black Sea, would be made available if needed during the Sochi Winter Olympics in support of Russia, which faces militant threats to disrupt the Games.

The Pentagon said U.S. military commanders were "conducting prudent planning and preparations" should American support be required during the Winter Olympics.

"The United States has offered its full support to the Russian government as it conducts security preparations for the Winter Olympics," Pentagon spokesman Rear Admiral John Kirby said in a statement.

"Air and naval assets, to include two Navy ships in the Black Sea, will be available if requested for all manner of contingencies in support of - and in consultation with - the Russian government."

The Pentagon statement came the same day that two men said by Islamist militants to have carried out suicide attacks in south Russia appeared in a video donning explosive belts and warning Russian President Vladimir Putin to expect a "present" at the Sochi Winter Olympics from fighters following after them.

Reuters reported on Sunday that U.S. military and intelligence officials have been studying contingency plans for evacuating Americans from the games in case of a crisis.

But U.S. officials have concluded there would be major obstacles to mounting a large-scale effort by the military or other U.S. government resources to evacuate Americans from Sochi, said a source familiar with Obama administration debates.

The most formidable roadblock U.S. officials have discussed regarding contingency plans for Sochi is that Russian authorities have historically been reluctant to allow foreign military forces, especially those of the United States, on Russian territory.

The State Department has warned Americans planning to attend the games to be vigilant about their security because of potential terrorist threats.

Owing to Sochi's location and the formidable security measures Russian authorities have put in place at the site, most U.S. intelligence experts say any attacks during the Olympics are most likely to occur at places other than Sochi.