President Donald Trump, joined by from left, Defense Secretary Mark Esper, and Chairman of the Joint Chiefs of Staff Gen. Mark…
FILE - President Donald Trump walks towards the Oval Office of the White House in Washington, Sept. 26, 2019.

Carla Babb at the Pentagon, Nike Ching at the State Department, National Security correspondent Jeff Seldin and Extremism Watch reporter Sirwan Kajjo contributed to this report.

WHITE HOUSE - U.S. President Donald Trump sent out a stern but conflicting warning Monday saying that U.S. troops would step aside for an expected Turkish attack on the Kurds, but he threatened to destroy the Turkish economy if they went too far.

"If they do anything outside what we think is humane," Trump told reporters Monday afternoon, "they could suffer the wrath of an extremely decimated economy."

The president's Republican allies expressed outrage at the prospect of abandoning Syrian Kurds who had fought Islamic State alongside U.S. troops.

One of Trump's most loyal supporters in the Senate on Monday called the decision "shortsighted and irresponsible."

FILE - Sen. Lindsey Graham, speaks to reporters after a briefing on Capitol Hill in Washington, May 21, 2019.

Appearing on the morning show "Fox & Friends," Republican Sen. Lindsey Graham was asked whether he supported the president's move.

"Absolutely not," he said, claiming the move was a "big win for ISIS." Graham said the Kurds in the area will align with Syrian dictator Bashar al-Assad because they'd have no choice. "So, this is a big win for Iran and Assad."

In response to a question from VOA about bipartisan concerns that Trump is effectively clearing the way for a Turkish massacre of the Kurds in Syria, a senior administration official said the U.S.'s action "is not a green light," and such assertions are "irresponsible."

Key lawmakers of both U.S. major political parties strongly condemned the president's decision.

Republican Senate Majority Leader Mitch McConnell and Democratic House Speaker Nancy Pelosi issued separate statements criticizing the move.

"A precipitous withdrawal of U.S. forces from Syria would only benefit Russia, Iran, and the Assad regime," McConnell said  

Pelosi called it a "deeply disturbing development that betrays our Kurdish allies who have been instrumental partners in our mission to eradicate" Islamic State.  

“...It is time for us to get out of these ridiculous Endless Wars, many of them tribal, and bring our soldiers home. WE WILL FIGHT WHERE IT IS TO OUR BENEFIT, AND ONLY FIGHT TO WIN,” Trump tweeted on Monday.

"Turkey, Europe, Syria, Iran, Iraq, Russia and the Kurds will now have to figure the situation out, and what they want to do with the captured ISIS fighters in their neighborhood," Trump said.

A senior administration official told reporters Monday  it would be Turkey's responsibility to both maintain the captivity of Islamic State fighters and to deal with "any sort of reconstitution of ISIS" that may occur.

After the widespread criticism that followed the administration's announcement Sunday that Turkey would be going forward with a Syria operation, Trump appeared Monday to reverse what was being viewed as his greenlighting of Turkish military action.

Pentagon and State Department officials have been voicing opposition to any such move by Turkey.

“Any uncoordinated military operation by Turkey would be of grave concern as it would undermine our shared interest of a secure northeast Syria and the enduring defeat of ISIS,” Pentagon spokesperson Commander Sean Robertson told VOA in an email.

On Monday, Turkey carried out airstrikes on alleged Kurdish PKK targets in Iraqi Kurdistan, multiple sources told  VOA.

One source described them as similar to "daily strikes" by Turkey in the area but added these likely meant to "test the waters" for more action in Syria.

FILE - U.S. Secretary of Defense Mark Esper speaks to reporters during a briefing at the Pentagon, Aug. 28, 2019.

A Pentagon official, speaking on condition of anonymity, told VOA that Defense Secretary Mike Esper was in contact over the weekend with the national security team (including Joint Chiefs of Staff Chairman Mark Milley, Secretary of State Mike Pompeo, National Security Adviser Robert O'Brien and the president) to discuss the situation in northern Syria.

"The Department of Defense made clear to Turkey — as did the president — that we do not endorse a Turkish operation in Northern Syria," said Assistant to the Secretary of Defense for Public Affairs Jonathan Hoffman. "The U.S. Armed Forces will not support or be involved in any such operation. "

A senior State Department official echoed that sentiment.

"We think this operation is a very bad idea. We do not think this operation will provide more security in the fight against Daesh [IS] for Turkey or for the people of the northeast," the official said.

Trump contends it is too costly to keep supporting U.S. allied Kurdish-led forces who "were paid massive amounts of money and equipment to do so. They have been fighting Turkey for decades."
 

The SDF says U.S. forces “have withdrawn from border areas with Turkey,” and they accused the United States of not fulfilling its responsibilities under a U.S.-Turkey agreement that involved the Kurdish fighters dismantling some of their defensive capabilities near the border to allay Turkish concerns. 

Turkey views the People's Protection Units (YPG), the main force within the SDF, as an extension of the Turkey-based Kurdistan Workers' Party (PKK), which has been fighting for greater rights in Turkey's Kurdish-majority southeast for decades.

FILE - Kurdish fighters from the People's Protection Units (YPG) run across a street in Raqqa, Syria, July 3, 2017.

The United States, however, makes a distinction between the PKK and YPG, backing the YPG-dominated SDF in the fight against Islamic State in Syria.

A spokesperson for the Syrian Democratic Council, the SDF's political wing, called the Trump administration decision “ill-conceived” and that Islamic State will “become a threat to the whole world,” with the questionable fate of Islamic State fighters in SDF custody becoming a “great danger” for the region.

“The situation over the ISIS detainees who are still organizing themselves while in SDF detention is not clear” according to Amjad Othman, a spokesman for the Syrian Democratic Council. “We repeatedly called for foreign states to take responsibility for their ISIS nationals. But there was no response.”

WATCH: Troop removal

Condemnations, Clarifications and Fear as Turks Start Syria Offensive video player.