U.S. President Donald Trump on Thursday praised Turkey's efforts to stop "carnage" in Syria's northwestern province of Idlib, accusing Russia, the Bashar al-Assad regime and Iran of killing "thousands" of innocents.

"Russia, Syria, and Iran are killing, or on their way to killing, thousands of innocent civilians in Idlib Province. Don't do it!" Trump said on Twitter.

"Turkey is working hard to stop this carnage," he added.

Trump stressed that the ongoing impeachment process against him also affected the external relations of the U.S., making it "more difficult" to deal with foreign leaders.

"Despite all of the great success that our Country has had over the last 3 years, it makes it much more difficult to deal with foreign leaders (and others) when I am having to constantly defend myself against the Do Nothing Democrats & their bogus Impeachment Scam," he said, adding: "Bad for USA!"

The House of Representatives approved impeachment against Trump on Dec. 18, accusing him of abuse of power and obstruction of Congress. He became the third president in U.S. history to be impeached.

Earlier this month, the U.S. Senate passed a $738 billion budget for the Pentagon which includes a mandate to impose sanctions within six months on Syria, Iran and Russia for their "war crimes" during the Syrian civil war.

Though not yet approved by Trump, the Caesar Syrian Civilian Protection Act of 2019 authorized additional sanctions and financial restrictions on institutions and individuals doing business with the Syrian regime.

Syria has been locked in a vicious civil war since early 2011, when the Bashar al-Assad regime cracked down on pro-democracy protests.

Since then, hundreds of thousands of people have been killed and more than 10 million others displaced, according to UN officials.

Idlib falls within a de-escalation zone laid out in a deal between Turkey and Russia in late 2018. The Syrian regime and its allies, however, have consistently broken the terms of the cease-fire, launching frequent attacks inside the zone.

The de-escalation zone is currently home to some four million civilians, including hundreds of thousands displaced in recent years by regime forces throughout the war-weary country.