By Warren Strobel and Jonathan Landay

WASHINGTON (Reuters) - U.S. President Donald Trump on Thursday thanked Russian President Vladimir Putin for ordering the United States to slash its diplomatic staff in Russia, remarks likely to rekindle criticism of Trump's kid-gloves handling of Putin.

Breaking nearly two weeks of silence on Putin's July 30 order cutting U.S. embassy and consulate staff by nearly two thirds, Trump said: "I'm very thankful that he let go of a large number of people because now we have a smaller payroll."

Trump said "there’s no real reason for them to go back" and "we're going to save a lot of money," in response to Putin's Cold War-style move, differing from the reactions of other presidents in similar circumstances in the past.

It also clashes with a State Department official having called Moscow's order "a regrettable and uncalled-for act."

On Thursday, the State Department had no immediate reaction to the comments Trump made to reporters while on vacation at his golf club in Bedminster, New Jersey.

Congressional committees and a special counsel are investigating the conclusions of U.S. intelligence agencies that Russia interfered in the 2016 election campaign by hacking and other methods to help Trump, a Republican. They are also looking into possible collusion between the campaign and Russian officials. Moscow has repeatedly denied meddling in the election and Trump denies any campaign collusion.

Putin, reacting to new sanctions imposed by the U.S. Congress and reluctantly signed into law by Trump, ordered Washington to cut 755 of its 1,200 embassy and consulate staff by September. Many of those affected likely will be local Russian staffers.

It was also a tit-for-tat reaction to former President Barack Obama expelling 35 Russian diplomats from the United States last December over the intelligence agency reports.

During his campaign and since becoming president, Trump has consistently called for better ties with Russia, declined to criticize Putin and refused to unequivocally embrace the conclusions of the intelligence agencies.

Intended to be flippant or not, Trump's remarks on Thursday were immediately denounced by current and former U.S. officials who have served both Republican and Democratic administrations.

Nicholas Burns, the State Department's third-ranking official under Republican President George W. Bush, called Trump's comments "grotesque."

"If he was joking, he should know better," said Burns, now a professor at Harvard University's John F. Kennedy School of Government. "If he wasn't, it's unprecedented. A president has never defended the expulsion of our diplomats."

The State Department has "horrified and rattled" by Trump’s remarks, said a veteran U.S. diplomat who has served in Russia, speaking on condition of anonymity.

And Heather Conley, formerly a top State Department official dealing with European affairs, said the expulsions of hundreds of people from an important U.S. embassy is extraordinary and "it is very difficult to see how the president could view these expulsions as a 'positive' development in any form."

In additional remarks on Thursday, Trump said he was surprised by the FBI raid last month on the home of his former campaign manager, Paul Manafort, adding that it sent a "strong signal."

Trump said he has not given any thought to the possibility of firing special counsel Robert Mueller. In May, Trump dismissed James Comey, who was Director of the FBI when Trump went into office seven months ago.

As presidential candidate, Trump invited Russia to dig up thousands of "missing" emails from Democratic rival Hillary Clinton's time as secretary of state, vexing intelligence experts and prompting Democrats to accuse him of urging a foreign country to spy on Americans.

"Russia, if you're listening, I hope you're able to find the 30,000 emails that are missing," Trump said on the campaign.

Clinton kept a private server from 2009 to 2013. She handed over thousands of emails in 2015 to investigators, but did not release about 30,000 she said were personal and not work-related.

(Additional reporting by Yeganeh Torbati and John Walcott; editing by Sandra Maler and Grant McCool)