Following their withdrawal, Turkeys military operation would be halted entirely, Pence said.

Great news out of Turkey, President Trump wrote on Twitter, shortly before Pences announcement. Millions of lives will be saved! he added.

Pences whirlwind trip to Turkey came just a week after the start of a military operation that had hastened the withdrawal of U.S. troops and scrambled alliances in Syrias volatile civil war. Turkeys western allies have warned Erdogan that the fighting could lead to the resurgence of the Islamic State militant group.

The Trump administration had faced criticism for the perception that it abandoned its own allies: the Syrian Kurdish militias who partnered with the U.S. military to fight the Islamic State. Turkey views the Kurdish fighters as a grave threat because of their links to militants in Turkey.

Pence said that the Kurdish fighters would honor the deal struck between the United States and Turkey. We have repeated assurances from them that they will be going out, he said, referring to the Syrian Kurdish fighters.

What Trump just triggered in Syria, visualized

You dont want to be responsible for slaughtering people, Trump wrote, concluding: Dont be a tough guy. Dont be a fool! The letter was written on the day Turkeys military operation started. Turkish officials told the BBC and other news outlets Thursday that Erdogan threw the letter in the trash. 

But the most clear answer to the letter that was written on October 9 was the Peace Spring Operation, CNN Turk reported, citing diplomatic sources and using Turkeys code name for its offensive. 

Erdogan said Wednesday that Turkey would never declare a cease-fire and vowed to forge ahead with plans to enforce a buffer zone as deep as 20 miles into Syrian territory. The swath of territory would stretch more than 280 miles from the northern city of Manbij to the Syrian border with Iraq. 

Trump has faced criticism, including from his own Republican allies, amid reports of a rushed U.S. troop withdrawal. 

The hasty U.S. pullback from Syria is a searing moment in Americas withdrawal from the Middle East

On Wednesday, the U.S. military withdrew from Raqqa, the former de facto capital of the Islamic State, as well as Tabqa and a major headquarters at the Lafarge Cement Factory in Jalabiya, Col. Myles B. Caggins III, a U.S. military spokesman, said in a tweet.

At the cement factory, after American troops had left, U.S. forces used F-15 jets to carry out airstrikes on parts of the headquarters to destroy an ammunition cache and reduce the facilitys military usefulness, Caggins wrote.

In addition to the ammunition, the strikes targeted a small compound that was ringed with blast walls and included living quarters and diesel power generators, said a U.S. military official, speaking on the condition of anonymity because of the sensitivity of the operation.

Lamothe reported from Washington.

Russia patrolling between Turkish and Syrian forces after U.S. troops withdraw

Trumps retreat in Syria turns into a mess

Trump tries to distance himself from chaos in Syria as tensions with lawmakers in both parties escalate