The State Department has lashed out at Brett McGurk, who resigned in protest at President Trump's Syria pull-out, accusing him of failing in his role as top U.S. diplomat for the coalition to defeat the Islamic State and lying about the timing of and reasons for his departure.

A senior State Department official derided McGurk, who was appointed by President Obama and has been in place since 2015, as ineffective. “The conflict in Syria has been ongoing for six years,” the senior State Department official said sarcastically. "Good job, Brett.”

Another source close to the circumstances surrounding McGurk’s resignation bitterly accused him of twisting the truth to increase the amount he could earn in speaking fees despite being treated “graciously” by Secretary of State Mike Pompeo.

As the State Depatment official and other supporters of Pompeo piled out, Trump himself tweeted scornfully about McGurk. “Brett McGurk, who I do not know, was appointed by President Obama in 2015,” the president tweeted Saturday evening. “Was supposed to leave in February but he just resigned prior to leaving. Grandstander? The Fake News is making such a big deal about this nothing event!”

Disputing the notion that McGurk had resigned on principle, the official said: “[He] was scheduled to leave the State Department in April of this year, but, asked the secretary to stay on. His departure was rescheduled for the end of this year, so for him to account for his departure to principle is unfounded.”

That contradicted McGurk, who submitted his resignation, effective December 31, on Friday. He said he was leaving early because of Trump’s shock decision. “The recent decision by the president came as a shock and was a complete reversal of policy that was articulated to us,” McGurk wrote in an email to colleagues, according to New York Times.

“I worked this week to help manage some of the fallout but — as many of you heard in my meetings and phone calls — I ultimately concluded that I could not carry out these new instructions and maintain my integrity.” Trump's tweet, however, stated McGurk was to leave in Februay, not at the end of 2018 as the State Department official insisted.

Sen. Chris Murphy, a member of the Foreign Relations Committee, responded to Trump in defense of McGurk. "Over the past 5 years, no one has done more to put ISIS on its heels than Brett," the Connecticut Democrat wrote. "We all know and rely on him. The fact that our President has no clue who Brett is should scare the hell out of every American."

But McGurk’s statement was self-serving, his critics maintain. “This guy should have been out on his ear back in April, and he was allowed to stay on because he basically needed the job,” the other source told the Washington Examiner on condition of anonymity.

“Now that he wants his speeches to collect $20,000 a pop instead of $2,000 a pop, he's trying to use this on the way out the door. That's what sucks about it.” Mattis’ departure has left the defense of the policy change to Secretary of State Mike Pompeo.

“We’ve made the caliphate in Syria go away,” Pompeo told NPR on Friday. “The president made an enormous commitment to take down the caliphate and that has been achieved.”

That statement put the focus on the Syria operations as a campaign against ISIS as a land-holding terrorist organization. McGurk, in what turned out to be his last briefing with the State Department press corps, argued against such thinking less than two weeks ago.

“We have obviously learned a lot of lessons in the past, so we know that once the physical space is defeated, we can’t just pick up and leave,” he told reporters on December 11.

“There’s clandestine cells. Nobody is saying that they are going to disappear. Nobody is that naive. So we want to stay on the ground and make sure that stability can be maintained in these areas.”

McGurk’s remarks were echoed days later by Ambassador James Jeffrey, whom Pompeo hired in August to serve as the special envoy for the negotiations to end the broader Syrian civil war. “ISIS will come back if the underlying conditions are receptive to that kind of ideological movement,” Jeffrey said on Monday.

Pompeo has acknowledged the need to continue counter-terrorism operations against ISIS.

"We will continue to keep the homeland safe from the threat from ISIS,” the top U.S. diplomat, who served previously as a Republican lawmaker from Kansas, said during a Thursday interview with KMUW, a Wichita-based public radio network. “But it no longer makes sense for there to be 2,000 soldiers stationed there. We can accomplish this mission in a different way.”

McGurk and Jeffrey have been the top two diplomats involved in the Syria crisis since August. Jeffrey is tasked with leading U.S. efforts to broker an ultimate political settlement to the Syrian civil war, a conflict that pits dictator Bashar Assad’s regime — backed by Russian air power and Iranian ground forces — against anti-Assad rebels, a shifting array of terrorist groups, and U.S.-backed local fighters. McGurk has spent the last three years coordinating the international coalition that liberated Iraqi and Syrian territory from the Islamic State.

“Where we were when the Trump administration came in – in early 2016 . . . about 50 percent of the territory had been cleared,” McGurk told reporters in his final briefing. “So if you look at where we are today, I think it’s quite significant. We really are now down to the last 1 percent of the physical territory.”