WASHINGTON — American and European intelligence and counterterrorism officials said on Tuesday that the escalating tensions between President Trump and President Recep Tayyip Erdogan of Turkey could jeopardize information sharing and law enforcement cooperation between the two countries as they fight the Islamic State in Syria.
Military commanders said plans were still underway for American and Turkish troops to conduct joint patrols near Manbij, a former Islamic State hotbed in northern Syria that was liberated by Kurdish fighters.
“That’ll start very soon,” Maj. Gen. Felix Gedney, the British deputy commander of the American-led coalition in Iraq and Syria, told reporters at the Pentagon.
But intelligence officials conceded that the most recent strain between Turkey and the United States — over American sanctions to punish Turkey for the detention of Andrew Brunson, an evangelical pastor from North Carolina — could halt new progress against the Islamic State.
A senior American intelligence official and a senior European counterterrorism official separately expressed concern that Turkey would withhold information about suspected Islamic State fighters and intelligence operations to root out extremists in Syria.
Additionally, they said, Turkey might obscure missions that its security forces are conducting to prevent foreign fighters from entering Syria. Both officials spoke on the condition of anonymity because they were not authorized to publicly discuss the matter.
The Americans have other reasons to worry about Turkey’s reliability as a battlefield partner.
Seth G. Jones, who leads the Transnational Threats Project at the Center for Strategic and International Studies in Washington, said Turkey had provided assistance to Hay’at Tahrir al-Sham, a jihadist group that has evolved from Jabhat al-Nusra, a Qaeda affiliate in northern Syria.
Mr. Jones said Turkey was using those jihadist groups to fight Kurdish forces in Syria. At least some of the Turkish support has been sent to extremists around Idlib, one of the last opposition strongholds that is now coming under fire from the Syrian government.
“A major concern is that while Turkey has taken some steps to root out cells of ISIS fighters, the Erdogan government has supported some other jihadist groups,” Mr. Jones said.
The Pentagon has for years sought to strike a balance between its NATO ally Turkey and the Kurdish fighters that have proved to be the most reliable ground force against the Islamic State in Syria.
Turkey believes the American-backed Kurdish fighters in Syria are linked to the Kurdistan Workers’ Party, or P.K.K., which both Turkey and the United States have designated as a terrorist organization.
Mr. Erdogan maintained on Tuesday that “there is no difference” between the Islamic State and the P.K.K.
“We do not discriminate between terrorist organizations,” Mr. Erdogan said at a news conference in Ankara, the Turkish capital. “There is no difference between ISIS’s butchers and P.K.K.’s murderers for us.”
At the moment, Kurdish and Turkish forces are each conducting patrols in Syria. While Turkish troops are securing Manbij, General Gedney said, American-backed Syrian Democratic Forces are preparing for a final assault on the Islamic State in the Hajin area, more than 200 miles away, and reinforcing checkpoints in the Middle Euphrates Valley.
Other specialists said that Turkey’s government had stiffened its border enforcement and efforts to root out Islamic extremists.
“Turkish policing of ISIS cells has been aggressive for years,” said Aaron Stein, a Turkey specialist at the Atlantic Council, a Washington think tank. “Turkish officials are cognizant of the dangers these men and women pose, following the wave of ISIS attacks that aggressive police action have largely stopped.”
As talks stall over Mr. Brunson’s release, the Trump administration is considering a range of further sanctions against Turkey — including limits on Turkish Airlines, according to a senior administration official who spoke on the condition of anonymity to discuss delicate negotiations.
The administration is also demanding the release of Serkan Golge, a NASA scientist who has been imprisoned for nearly a year, and three Turkish citizens who worked for the State Department in Turkey, the official said.
But the official said that if Mr. Brunson was not released by Wednesday, more sanctions could soon be put in place.
“Certainly the president has a great deal of frustration on the fact that Pastor Brunson has not been released, as well as the fact that other U.S. citizens and employees of diplomatic facilities have not been released,” Sarah Huckabee Sanders, the White House press secretary, told reporters on Tuesday. “And we’re going to continue to call on Turkey to do the right thing and release those individuals.”
Additionally, during a meeting on Monday at the White House, Turkey’s ambassador to the United States asked for concessions for the Turkish state-owned bank, known as Halkbank, and one its executives, according to a person familiar with the conversation.
The bank is under investigation by the United States Treasury Department on suspicion of violating sanctions against Iran. One of the bank’s top executives, Mehmet Hakan Atilla, is serving time in an American prison after being convicted of charges related to helping orchestrate a billion-dollar scheme to evade the sanctions.
The Turks have sought leniency in the sanction process, and the extradition of Mr. Attila to serve a prison sentence in Turkey.
Gardiner Harris, Kenneth Vogel and Adam Goldman contributed reporting from Washington, and Carlotta Gall from Istanbul.