Following the alleged gas attack in Syria, retaliatory military action could be waged by the US, UK and France against Bashar Assad's government - who denies the use of chemical weapons.
US President Donald Trump promised that the attack will be "met forcefully" and that missiles will be "coming".
Russia previously said that a US air strike on Syria would be seen as a war crime that could trigger a military clash between the two countries.
In response, the Kremlin has vowed to shoot down any missiles aimed at Syria using its lethal anti-aircraft system, the S-400 Triumf.
Called the SA-21 Growler by NATO, the S-400 is a fourth-generation mobile long-range missile defence system developed by Russia.
Fear about the use of the S-400 have increased after Russia's ambassador to Lebanon Alexander Zasypkin said in an interview: "If there is a strike by the Americans, then... The missiles will be downed and the source of the missiles targeted".
Speaking to al-Manar TV, he suggested that they could hit "even the sources that launched the missiles".
The S-400 is currently deployed in Kaliningrad, Syria and Crimea, and can shoot up to 80 targets simultaneously.
Russia says it has a range of 248 miles, which means that from its location near Latakia, in Syria, it could reach Lebanon, much of Israel, Jordan and the eastern Mediterranean.
-- Manufacturer: Almaz-Antey arms firm
-- Range: 248 miles
-- Speed: up to 4.8km (3 miles) per second
-- Max target height: 30km - can track up to 80 targets simultaneously
-- Missiles: primarily 48N
-- Types of target: aircraft, drones, cruise and ballistic missiles, ground objectives, as well as other airborne surveillance systems.
The S-400 was initially deployed in Syria at its air force base near Latakia in December 2015, after Turkish jets downed a Russian bomber on the Syrian-Turkish border.
It is currently being marketed to other countries, such as China, India and Turkey, which have purchased respectively six and five battalions of the system.
However, according to the Center for Strategic and International Studies (CSIS), Russia is now developing a new interceptor, the 77N6, which is believed to employ hit-to-kill technology.