Russia's prime minister said Friday that the country could dissolve all diplomatic ties with neighboring Ukraine in light of recent security concerns.
"If there is no other way to change the situation, the president could take this step," state media quoted Dmitry Medvedev as saying.
The move wasn't previously proposed after Russia annexed Crimea in 2014, or when Moscow supported separatist rebels in eastern Ukraine.
Russia has deployed an advanced air defense missile system to Crimea, the military said in a statement Friday. The French news agency reports the anti-aircraft S-400 system is capable of tracking some 300 targets and shooting down nearly three dozen simultaneously.
Ukrainian troops are on high alert as tensions with Russia rise. Ukraine accuses the neighboring country of increasing its troop presence on the Crimean peninsula. Russia accuses Ukraine of plotting to wage attacks in the disputed peninsula with what the Russians call "terrorist attacks," but Ukraine denies these clashes took place.
Russia's annexation of the peninsula has been condemned by world leaders.
Carolyn Presutti contributed to this report