FILE - U.S. and Turkish soldiers conduct the first-ever combined joint patrol outside Manbij, Syria, Nov. 1, 2018, in this U.S. Army handout photo provided by Reuters.
FILE - U.S. and Turkish soldiers conduct the first-ever combined joint patrol outside Manbij, Syria, Nov. 1, 2018, in this U.S. Army handout photo provided by Reuters.

In a series of tweets early Thursday, President Donald Trump defended his decision to start withdrawing U.S. troops from Syria, saying the U.S. does not want to be "the Policeman of the Middle East."

Responding to criticism from legislators and pundits, Trump says the U.S. presence in Syria is getting the U.S. "NOTHING but spending precious lives and trillions of dollars protecting others who, in almost all cases, do not appreciate what we are doing?"

The president described Russia, Iran and Syria as the "local enemy of ISIS" and said "we were doing there [sic] work."

Without offering specifics, Trump declared a U.S. victory Wednesday over the Islamic State terror group, which was followed by a White House announcement the U.S. had started bringing U.S. troops in the war-torn country back home. 

Until now, U.S. troops in Syria had been working closely with an alliance of Kurdish and Arab militias known as the Syrian Democratic Forces. White House officials maintain the SDF and other partner forces will be responsible for eliminating the last pockets of IS-controlled territory.

The SDF issued a statement Thursday, though, rejecting Trump's assertion that Islamic State has been defeated, and saying a U.S. withdrawal would allow for a resurgence of the group.

Russian President Vladimir Putin welcomed Trump's decision Thursday, reiterating his government's position that U.S. forces were not welcome in Syria. He also cited the U.S. presence in Afghanistan to express skepticism about whether the troops deployed in Syria would actually leave.

FILE - U.S. forces are seen at the Kurdish People's Protection Units (YPG) headquarters after it was hit by Turkish airstrikes in Mount Karachok near Malikiya, Syria, April 25, 2017.
Syria: What’s at Stake for US, Russia, Iran and Turkey
The announcement Wednesday by the White House that the U.S. has defeated Islamic State (IS) in Syria and begun withdrawing troops from the country took many by surprise.The Syrian civil war, now in its eighth year, is further complicated by the actions within its borders by four other countries: the U.S., Russia, Iran and Turkey. FILE - Syrian schoolchildren walk as U.S. troops pFILE - Syrian schoolchildren walk as U.S. troops patrol near the Turkish border…

Trump's announcement Wednesday triggered a stream of criticism from some defense and diplomatic officials, as well as lawmakers, who were surprised. "It blindsided me," said South Carolina Republican Sen. Lindsey Graham, usually a Trump ally.

"We have started returning United States troops home as we transition to the next phase of this campaign," White House Press Secretary Sarah Sanders said, adding the defeat of IS did not mean the military campaign by coalition forces is ending in Syria.

Hours later, Pentagon spokesperson Dana White said in a statement "the coalition has liberated ISIS-held territory, but the campaign against ISIS is not over." 

By late Wednesday, Trump weighed in again, releasing a video statement. "We have won against ISIS. We've beaten them and we've beaten them badly," the president said.

Neither the White House nor the Pentagon would say how long it would take to safely withdraw all U.S. forces from Syria. White House officials also said that IS fighters continue clinging to one last pocket of territory in northeastern Syria, though they insist the terror group was not mounting enough resistance to postpone a declaration of victory.

IS Fighters in Syria

Just last week, Brett McGurk, U.S. special presidential envoy for the Global Coalition to Defeat ISIS, told reporters at the State Department that liberating the last one percent of IS-held territory could take "a period of months."

Pentagon estimates from August of this year also warned IS still had at least 13,000 fighters in Syria, where the caliphate had already collapsed.

A member of the Iraqi forces walks past a mural bearing the logo of the Islamic State group in a tunnel that was reportedly used as a training center by the jihadists, on March 1, 2017, in the village of Albu Sayf, on the southern outskirts of Mosul.
Far From Dead: Tens of Thousands of IS Fighters Linger in Iraq, Syria    
The Islamic State terror group may be far more resilient, stronger and dangerous than U.S. officials have been willing to let on, boasting a fighting force in Iraq and Syria that comes close to what it fielded at its peak.After four years of bombings, the elimination of key IS leaders, and other U.S.

Defense Secretary Jim Mattis and other senior U.S. officials also have been advocating for a longer-term military presence in Syria to help ensure IS cannot re-emerge as a force in the Middle East.

The U.S. withdrawal also raises questions about the fate of hundreds of IS foreign fighters who have been taken prisoner and are currently in SDF custody. Many governments have refused to take them back, and there is a chance what is left of the SDF could set them free without the prospect of any U.S. support.

International reaction to the U.S. announcement has been mixed, with Britain noting progress made in the fight against IS and France pledging to continue the fight.
As for the next phase of the U.S. fight against IS, administration officials said there is no illusion the threat from IS is gone, but said the focus will move to Libya and Egypt's Sinai Peninsula.

A total pullout of U.S. troops from Syria would still leave the U.S. military with a sizable presence in the region, including more than 5,000 troops in neighboring Iraq.

VOA's Persian and Kurdish Services contributed to this report.