US Senate majority leader Mitch McConnell has called President Donald Trump's decision to pull out troops from Syria "a strategic nightmare" for Washington's allies, such as Israel and Jordan.
"Withdrawing US forces from Syria is a grave strategic mistake," McConnell, the top Republican in Congress, wrote in an op-ed published in The Washington Post on Friday.
"It will leave the American people and homeland less safe, embolden our enemies, and weaken important alliances,” he added.
Turkey last week began pounding the positions of Kurdish fighters with jets and artillery and sent in troops to purge them from the area east of Euphrates.
The offensive came three days after Trump announced he would pull US troops from the region, effectively exposing its allied Kurdish militants to their archenemy, Turkey.
Trump defended his decision to pull US troops out of Syria as "strategically brilliant."
McConnell has condemned Trump's withdrawal of troops from northeast Syria.
Fighting has continued despite a temporary ceasefire Vice President Mike Pence brokered with Turkish President Recep Tayyip Erdogan.
"The combination of a US pullback and the escalating Turkish-Kurdish hostilities is creating a strategic nightmare for our country," McConnell wrote in his article.
"Even if the five-day ceasefire announced Thursday holds, events of the past week have set back the United States' campaign against [Daesh] and other terrorists," he said.
On Thursday, US Vice President Mike Pence said Washington and Ankara had agreed on a five-day ceasefire in Turkey's attacks on Kurdish fighters in the region. The agreement followed negotiations between Pence and Erdogan at the presidential palace in Ankara.
Pence said Ankara would halt its offensive, dubbed Operation Peace Spring, for 120 hours in order to allow Kurdish fighters from the People's Protection Units (YPG) to withdraw 30 kilometers from the Turkey-Syria border.
"We saw [Daesh] flourish in Iraq after President Barack Obama's retreat. We will see these things anew in Syria and Afghanistan if we abandon our partners and retreat from these conflicts before they are won," McConnell wrote.
McConnell’s remarks come as Secretary of State Mike Pompeo has said Israel has "fundamental rights" and retains "operational freedom" to operate in Syria.
Israeli politicians have expressed concerns that the US pullout from Syria will further strengthen Iran’s position as a regional power at a time when Damascus is eliminating the last remnants of terrorists and reasserting control over all the country.