SULAIMANI (ESTA) — The United States has reduced the number of partnered patrols in northern Syria with Syrian Democratic Forces (SDF), the Pentagon said on Tuesday, after Turkish strikes in the region and ahead of a feared ground invasion by Ankara.

Pentagon spokesman Brigadier General Patrick Ryder told reporters that while operations against Islamic State had not stopped, the patrols had to be reduced because the SDF had reduced the number of their own patrols.

Ryder added that U.S. Defense Secretary Lloyd Austin would speak with his Turkish counterpart soon.

Turkish officials said the army needed just a few days to be ready for a ground incursion into northern Syria, which has been attacked with howitzer long-range weapons and warplanes by the Turks for days.

The bombardments come after months of threats by Turkish President Tayyip Erdogan of a new ground invasion against Kurdish forces, which he considers to be terrorists.

Syrian Kurdish forces have received backing from Washington for years, but have also coordinated with Syria’s government and its ally Russia, both seen as foes by the United States.

The Commander-in-chief of the U.S.-backed SDF said Tuesday he still feared a Turkish ground invasion despite U.S. assurances and has demanded a “stronger” message from Washington after seeing unprecedented Turkish deployments along the border.

“There are reinforcements on the border and within Syria in areas controlled by factions allied to Turkey. We noticed this and, yes, this is new,” SDF chief Mazloum Abdi told Reuters via phone from Syria.

“We are still nervous. We need stronger, more solid statements to stop Turkey,” he said. “Turkey has announced its intent and is now feeling things out. The beginning of an invasion will depend on how it analyses the positions of other countries.”