Trump's remarks to CNN television yesterday came the same day Russian warplanes began air raids in Syria's centre and north -- their first military engagement outside the former Soviet Union since the occupation of Afghanistan in 1979.
"Look, if Russia wants to go in there, would have been nice if we went in as a unified front, to be honest. But if Russia wants to go in there and knock out ISIS and maybe stabilise, this big migration with 200,000 people into the United States..." Trump said.
"We're not going to accept 200,000 people that may be ISIS. We have no idea who they are. And I'm telling you now, they may come in through the weakness of (President Barack) Obama," but would return to their homeland if Trump makes it to the White House, he said.
The Americans accused Russia of striking moderate rebel factions fighting Bashar al-Assad's Syrian regime under cover of their claimed assault on the Islamic State group.
The Pentagon says Russia has in recent weeks sent troops, warplanes and other military hardware to Syria.
