WASHINGTON (AP) — President Donald Trump said Wednesday the U.S. does not endorse Turkey's military assault on Syria, calling the operation a "bad idea."

Trump's written statement was issued hours after Turkey, a NATO ally, launched an offensive against Kurdish fighters in Syria, who have helped the U.S. against the Islamic State but are viewed by Turkey as terrorists. Trump's recent decision to pull back U.S. troops leaves those fighters vulnerable.

"The United States does not endorse this attack and has made it clear to Turkey that this operation is a bad idea," Trump said.

He said no American soldiers are in the area.

"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," Trump added. "Turkey has committed to protecting civilians, protecting religious minorities, including Christians, and ensuring no humanitarian crisis takes place_and we will hold them to this commitment."

He said the U.S. will monitor the situation closely.

Earlier Wednesday, Trump lashed out over sharp criticism of his decision to pull back U.S. troops from northeastern Syria, insisting he is focused on the "BIG PICTURE" that doesn't include American involvement in "stupid endless wars" in the Middle East.

"Fighting between various groups that has been going on for hundreds of years. USA should never have been in Middle East," Trump said in a series of tweets. "The stupid endless wars, for us, are ending!"

Trump's words are at odds with longstanding U.S. policy of keeping thousands of American troops in the strategically important region, and his decision is being condemned by some of his staunchest Republican allies.

Sen. Lindsey Graham, R-S.C., a close Trump ally, stepped up his criticism of the president Wednesday, telling "Fox & Friends" that if Trump "follows through with this, it would be the biggest mistake of his presidency."

In tweets, Graham urged prayers for "our Kurdish allies who have been shamelessly abandoned by the Trump Administration," adding, "This move ensures the reemergence of ISIS." He also said he would lead an effort in Congress to "make Erdogan pay a heavy price," referring to Turkish President Recep Tayyip Erdogan.

Another Trump ally, Rep. Liz Cheney of Wyoming, a member of the GOP leadership, said she was sickened by the prospect of a Turkish incursion. "Impossible to understand," she tweeted, why Trump "is leaving America's allies to be slaughtered and enabling the return of ISIS."

Trump argued on Twitter that "GOING INTO THE MIDDLE EAST IS THE WORST DECISION EVER MADE IN THE HISTORY OF OUR COUNTRY!" He said the U.S. went to war under a "false & now disproven premise, WEAPONS OF MASS DESTRUCTION. There were NONE!"

Trump said he is "slowly & carefully" bringing home "our great soldiers & military," in line with his campaign promise to do so.

His call for ending U.S. military involvement in the Middle East and bringing the troops home was a feature of his presidential campaign, but it flies in the face of many decades of bipartisan American policy, even as the Trump administration and its immediate predecessor have tried to give additional attention to what they see as long-term security threats elsewhere, including from China and Russia.

The U.S. has more than 10,000 troops based across the Middle East, including about 5,200 in Iraq, 1,000 in Syria and several thousand others at bases in Kuwait, the United Arab Emirates and Qatar. Also, the U.S. Navy's Mideast headquarters is at Bahrain in the Persian Gulf.

Just a couple of months ago the Pentagon reestablished a troop presence in Saudi Arabia after a lengthy absence, and in May it added air and naval forces in the region in response to what it views as worrying threats from Iran.

As a further sign that the military does not share Trump's view that the fight against the extremists is over, a press release Wednesday by the U.S.-led military coalition combating IS highlighted recent battlefield gains. It concluded by saying that "removing" IS fighters, weapons and bomb materials "remains a top priority" as the group "continues to plot attacks against innocent civilians and our partners throughout Iraq and northeast Syria."

Trump has long criticized President George W. Bush's decision to invade Iraq in 2003, but the subsequent rise of extremist groups like the Islamic State has convinced many national security officials, and lawmakers such as Graham, that a precipitous U.S. troop withdrawal from the region would leave the U.S. and its allies even more vulnerable to extremism.

Trump also claimed the U.S. has spent $8 trillion "fighting and policing" in the Middle East, up from the $7 trillion figure he has cited numerous times.

Trump is using an inflated estimate on the cost of wars and referring in part to predicted costs going decades into the future, not money actually spent. Some of the spending also reflects his policy decisions he made since taking office nearly three years ago.

Graham said Congress "will push back" against Turkey. He had said earlier this week that he was working on a bipartisan bill to sanction Turkey if they invade Syria.

"We're not giving Turkey a green light in Congress and we're not going to abandon the Kurds," he said.

Trump announced Tuesday that he and Erdogan will meet at the White House on Nov. 13.