Former U.S. Ambassador to Russia Michael McFaul railed against President Trump on Thursday after he thanked Russian President Vladimir Putin for ordering the U.S. to cut its diplomatic staff by 755 people.

In his first comments on the move by Russia, Trump said he was thanking Putin because the decision allows the U.S. government to "cut down our payroll."

"I want to thank him, because we're trying to cut down our payroll, and as far as I'm concerned I'm very thankful that he let go of a large number of people because now we have a smaller payroll," Trump told reporters at his Bedminster, N.J., golf club.

McFaul tweeted about the comments Thursday night.

"Trump just applauded cuts of 755 in Russian embassy. Maybe he should look to trim his own staff?" McFaul tweeted.

"You realize Mr. President that the State Dept organizes US delegations to GES -- those same people you just said were not needed in Russia. Our diplomats, professional staff, and military serving in Russia provide Washington with invaluable information about Russia," he continued over a series of tweets.

"Imagine wanting to know less about Russia's military modernization! That's what Trump praised today. Imagine wanting to know less about Russian foreign policy intentions and plans!" McFaul added. "That's what embassy personnel reductions will do. Imagine dissing Americans --patriots serving our country under difficult conditions in Russia -to praise Putin. Our president did today."

McFaul, who served as ambassador from 2012 to 2014, has previously spoken out against the Trump administration, saying in May this year that he thinks "Russians are laughing" at the U.S.

"I think the Russians are laughing," he said in an interview on MSNBC. "I think that's right, but they're laughing at how easy it is. And how our president, unfortunately, is helping with their agenda."