General Mazlum Kobane told NBC that the pullout of U.S. troops and the agreement to a buffer zone could have catastrophic consequences for the Kurds.
A New Yorker cartoon by Joe Dator reimagines Trump's October 9 missive to the Turkish president as if he were writing to Santa Claus.
In the letter, Donald Trump urged the Turkish president to "not be a tough guy" over the conflict in Syria.
Dozens of nations see the deaths of a million and a half Armenians and hundreds of thousands of Greeks and Assyrians under the Ottomans as a genocide, the U.S. might have too, an NSC official told Newsweek.
Andrei Kozyrev told MSNBC that the Kremlin was right to celebrate Trump's election in 2016 because he has handed the advantage to Putin in Syria.
Trump whipped up a crowd of supporters in Dallas on Thursday by claiming credit for the five-day "ceasefire" in northeastern Syria.
The Democratic senator described Trump's missive to Turkey's president as "one heck of an interesting letter."
Trump made the comments during a press conference with Italian President Sergio Mattarella on Wednesday.
Sources close to the Turkish leader told BBC News that Erdogan "thoroughly rejected" the letter dated last Wednesday and chucked it in the trash.
The House Speaker told reporters that the meeting between top Democrats, Republicans and the president was "most unsatisfactory."
U.S. president sent the letter on October 9 telling his Turkish counterpart 'Don't be a fool' over Ankara's incursions into northern Syria after the pullout by U.S. troops.
White House correspondent for the New York Times Katie Rogers Tweeted a scan of a letter that was confirmed to be a genuine missive from President Trump, sent to the President of the Republic of Turkey, Tayyip Erdogan.
"We should in a bipartisan way seek to ... change Turkey's behavior," Democratic Representative Eric Swalwell said.
Some 50 U.S. warheads are believed to be deployed at the Incirlik air base in southern Turkey, but reports this weekend suggested officials were reviewing plans for their removal.
"At a certain point, Turkey reached its limit," Turkish leader Recep Tayyip Erdogan said, regarding the influx of refugees from Syria into Turkey as a result of a brutal civil war raging in the country.
Trump's business ties in Turkey have raised concerns that White House policy is being influenced by the president's own commercial interests.
Michael S. Smith II said that by allowing the Turkish invasion into northeastern Syria, Trump and Erdogan have played into Putin's hands.
The South Carolina senator and Trump ally slammed the president last week over the withdrawal of U.S. military support in Syria.
Trump gave Turkey the green light to invade northeastern Syria after a phone call with Turkish President Erdoğan last Sunday.
"We've won. We've beat ISIS and we've beat them badly and decisively," the president told reporters last week.
The president's comments come amid widespread criticism and accusations he betrayed the Syrian Kurds.
"This is heart-rending for anybody who has shed blood, who has deployed forward," former NATO Supreme Allied Commander James Stavridis said.
"We learnt that President Trump has ordered the U.S. military not to help," Fox News National Security Correspondent Jennifer Griffin said.
"Remember that earlier this year, Trump VETOED Congress' attempt to end US involvement in the Yemen War," the Democratic congresswoman tweeted.
Despite loud protests about American betrayal, core U.S. national security interests in war-ravaged Syria were always narrow and specific: destroy the Islamic State's physical caliphate.
"The fight against Daesh [ISIS] is not over and continues alongside the [Kurdish-led] Syrian Democratic Forces," Prime Minister Edouard Philippe said.
Just hours after Trump threatened to "obliterate" Turkey's economy, he described the country as one of America's biggest and most honest trading partners
"We are voluntarily abdicating our role and it's the Russians, Iranians and others who are benefitting," Richard Haass warned.
"I am absolutely appalled that the United States is going to betray those Democratic forces in northern Syria," Pat Robertson said on "The 700 Club."
"The president has shown on a range of foreign policy efforts that he thinks of these things primarily in terms of optics and political calculus back home," Hoffman said. "The difference in this case is the Turks really are going to go in."