The White House is insisting that President Trump did not offer Turkey a “green light” to slaughter U.S.-backed Kurdish forces in northern Syria last night and that the U.S. wouldn't bear responsibility for any Islamic State resurgence in the area.

Why it matters: Confusion and concern followed the sudden announcement last night — after a call between Trump and Turkish President Recep Tayyip Erdoğan — that the U.S. would withdraw from the “immediate area” into which Turkish troops are expected to advance.

Turkey fiercely opposes the primarily Kurdish forces that hold the area and helped the U.S. retake swathes of Syria from ISIS, leading to bipartisan accusations that Trump is abandoning an ally.

The backlash included Sens. Lindsey Graham, Marco Rubio, Mitch McConnell, House Minority Leader Kevin McCarthy and former UN Ambassador Nikki Haley.

There was an information vacuum for much of the day beyond the tweets in which Trump reiterated his desire to leave Syria, claimed the Kurds had been "paid massive amounts" to fight ISIS and warned he would "destroy and obliterate" Turkey's economy if it did anything he found "off limits."

Expand chart Data: Conflict Monitor by IHS Markit as of Oct. 7; Map: Lazaro Gamio/Axios

The latest: A senior administration official told reporters on a call tonight that Trump was withdrawing 50–100 special forces troops currently operating near the Turkey-Syria border, but not pulling out of Syria entirely.

The official said Trump had determined Erdoğan was “set on undertaking an operation in northern Syria” after months of threats and said Trump didn’t want U.S. troops in the path of a NATO ally.

The official said repeatedly that Trump was not endorsing Erdoğan’s plan, but wouldn’t say whether he’d warned him not to move ahead.

Kurdish forces are guarding camps that hold thousands of suspected ISIS fighters and have warned they may have to abandon them to counter Turkey.

The White House says Turkey would then be "responsible for maintaining the captivity of those fighters" and would bear "full responsibility" if ISIS rebounds in the area.

Between the lines: Jennifer Cafarella of the Institute for the Study of War tells Axios that whether this "spirals into a broader regional war" depends on how the Kurds react to what will likely be a "limited" initial Turkish incursion. The most serious risks for them extend beyond war to potential ethnic cleansing.

The big picture: The senior U.S. official said this was “not the beginning of a formal pullout of Syria,” but added that both Trump and the American people “want our troops home as soon as possible.”

“The president has been transparent in his desire to get out of the region, which immediately changes everybody's calculus," Cafarella says. "Most of our adversaries are currently running down the clock expecting that at some point we will leave.”

Trump, for his part, says that was always the plan. He tweeted that the U.S. would only fight "WHERE IT IS TO OUR BENEFIT" and that if ISIS returns, "we can always go back & BLAST!"

Go deeper: Top Kurdish commander says Trump's Syria move puts victories over ISIS at risk