President Donald Trump speaks Tuesday during a ceremony to present the Presidential Medal of Freedom to former Attorney General Edwin Meese in the Oval Office of the White House in Washington. Credit: Alex Brandon | AP

President Donald Trump urged Turkey on Wednesday to protect civilians and safeguard Islamic State group prisons as it launched a military operation in northern Syria against Syrian Kurdish forces, saying the United States would hold its NATO ally responsible for the consequences of its decision to attack a key U.S. counterterrorism partner.

Calling the offensive “a bad idea,” the president said in a statement that Turkey had promised to avert a humanitarian crisis and ensure its operation did not allow the Islamic State to regain strength.

“We expect Turkey to abide by all of its commitments,” Trump said.

The president also linked his decision to withdraw U.S. forces from the area now being targeted by Turkey — a move widely criticized as enabling the Turkish attack — to his goal of ending the insurgent wars that have dominated the U.S. military’s focus for two decades.

“From the first day I entered the political arena, I made it clear that I did not want to fight these endless, senseless wars — especially those that don’t benefit the United States,” he said.”

Earlier in the day, Trump noted on Twitter that U.S. forces “should never have been there in the first place.”

The president’s remarks came as Republicans in Congress continued to warn that the Turkish assault was a threat to U.S. policy interests.

“A Turkish military advance into Syria threatens to halt momentum against ISIS, directly assaults our SDF partners, and could give the likes of al-Qaida and Iran new footholds in the region,” U.S. Rep. Kevin McCarthy, R-California, tweeted. He called on Turkey to “stop immediately and continue to work with the US to secure the region.”

ISIS is an acronym for the Islamic State group. The SDF refers to the Syrian Democratic Forces, the Kurdish-dominated fighters who have been the principal U.S. allies on the ground against the militants.

U.S. Sen. Lindsey Graham, R-South Carolina, a close Trump ally, noted that “It’ll be hard to protect America without allies over there, and the Kurds have been good allies.” The Turks were not entering Syria to fight the Islamic State group, Graham said on Fox & Friends on Wednesday morning. “They’re going in to kill the Kurds.”

Speaking of Trump, Graham said, “I hope he’s right. I don’t think so. I know that every military person has told him don’t do this.”

U.S. Rep. Liz Cheney, R-Wyoming, said the withdrawal of U.S. forces from northern Syria was having “sickening and predictable consequences.”

“The U.S. is abandoning our ally the Kurds, who fought ISIS on the ground and helped protect the U.S. homeland,” she said in a statement. “This decision aids America’s adversaries, Russia, Iran, and Turkey, and paves the way for a resurgence of ISIS.”

U.S. Sen. Susan Collins, a Republican who on Monday called Trump’s troop withdrawl “terribly unwise,” on Wednesday reiterated her criticism, saying “we are seeing the consequences of that terrible decision.”

“If the reports of Turkish strikes in Syria are accurate, I fear our allies the Kurds could be slaughtered,” Collins said.

The other members of Maine’s congressional delegation — independent U.S. Sen. Angus King and Democratic U.S. Reps. Chellie Pingree and Jared Golden — all lined up in opposition to the troop withdrawal, a move they said abandons a U.S. ally in the fight against extremism in the Middle East.

Meanwhile, the U.S. military was closely monitoring the events. One U.S. official, who like others was not authorized to discuss the situation publicly, said the Pentagon was tracking Turkish airstrikes in the region, including some that appeared to hit populated areas.

The official said the SDF had reduced its presence at prisons in Syria where thousands of Islamic State group fighters are being held and at other camps for displaced people that it controls.

Later in the day, an official said all operations focused on the Islamic State in Syria had been halted at this time.

NATO Secretary General Jens Stoltenberg said Turkey, a NATO member, had informed the alliance about its “ongoing operation in Northern Syria.”

“I count on Turkey to act with restraint & ensure that the gains we have made in the fight against ISIS are not jeopardized,” Stoltenberg said on Twitter. “I will discuss this issue with [Turkish] President Erdogan Friday.”

U.S. officials said Turkish defense officials had also notified a U.S. general based in Ankara as Washington’s military attache early Wednesday that Turkey’s operation in Syria would begin within a few hours. Turkish forces began pressing forward not long afterward.

The situation raises questions for U.S. troops in both Syria and Turkey.

The U.S. military established a combined joint operations center in Ankara several weeks ago to coordinate with Turkish forces on patrols in a “security mechanism” buffer zone in Syria along the border with Turkey. With Turkey turning away from that agreement, however, the U.S. troops at the center may be called on to instead monitor the Turkish operation and make sure that U.S. troops stay out of harm’s way, the U.S. officials said.

In a sign of Washington’s disapproval, Turkish forces were removed from planned flights by the U.S.-led military coalition against the Islamic State group in Syria, officials said. Turkish access to some intelligence and surveillance information also has been curtailed.

BDN writer Christopher Burns contributed to this report.