President Donald Trump threw down the gauntlet Wednesday morning by telling Russia to prepare for a US missile strike on Syria in response to a suspected chemical weapons attack blamed on the Syrian government.

A Russian diplomat had previously threatened to shoot down US missiles, and the platforms firing them, if the US attacked Syria.

But the Kremlin has urged caution, trying to talk the US down from a strike on Syria.

President Donald Trump threw down the gauntlet Wednesday morning by telling Russia to prepare for a US missile strike on Syria in response to a suspected chemical weapons attack blamed on the Syrian government.

"Russia vows to shoot down any and all missiles fired at Syria. Get ready Russia, because they will be coming, nice and new and 'smart!'" Trump tweeted. "You shouldn't be partners with a Gas Killing Animal who kills his people and enjoys it!"

The first part of Trump's tweet referred to comments by Russia's ambassador to Lebanon, Alexander Zasypkin, who effectively threatening to shoot down or sink any US planes or ships that open fire.

"If there is a strike by the Americans," Zasypkin told the militant group Hezbollah's Al-Manar TV, then "the missiles will be downed and even the sources from which the missiles were fired."

Vladimir Shamanov, a defense committee chairman in the Russian legislature's lower house, also said on Tuesday that the US would face "grave repercussions" for a strike on Syria.

When the US struck a Syrian air base over a suspected chemical attack in April 2017, it used Tomahawk missiles launched from US Navy guided-missile destroyer ships.

"The Russian military in Syria has air-defense systems theoretically capable of shooting down US Tomahawk missiles," Justin Bronk, an air-combat expert at the Royal United Services Institute, told Business Insider.

But, according to Bronk, a large salvo of US missiles could overwhelm the defenses, which he said were "largely unproven in actual combat use."

Also, because of the extremely high stakes a conflict between the US and Russia would entail, Bronk said Russia was "extremely unlikely to actually attack US ships or aircraft outside of Syrian territory, if at all."

The Kremlin's official line has been to press for calm.

"We would like to hope that all sides will avoid any steps that a) are not provoked by anything and b) could significantly destabilize an already fragile situation in the region," the Kremlin spokesman Dmitry Peskov told a conference call with reporters, according to Reuters.