President Trump Donald John TrumpFederal prosecutor speaks out, says Barr 'has brought shame' on Justice Dept. Former Pence aide: White House staffers discussed Trump refusing to leave office Progressive group buys domain name of Trump's No. 1 Supreme Court pick MORE this week showed no sign of backing down on his decision to withdraw U.S. troops from northern Syria, stoking fears in Washington of worst-case scenarios from abandoning a crucial defense partner.

Trump's move, which has paved the way for Turkey to proceed with a long-planned offensive against Syrian Kurdish forces who were instrumental in the fight against ISIS, has far-reaching implications both at home and abroad.

Critics, including many from Trump's own party, argue the president is irreparably damaging the country's standing as a reliable partner by abandoning a U.S. ally, the Syrian Democratic Forces (SDF), to be slaughtered by Turkey as well as fueling mayhem in the region that could allow ISIS to regain its footing.

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Trump, however, has pushed ahead, insisting the Kurds have mostly been fighting for their land and that he is filling a campaign promise to end “forever wars.”

Here are five reasons Trump's move could spell trouble.

ISIS fight upended, threatening a resurgence

In moving back from the Syria-Turkey border, U.S. troops left their Kurdish partners to both guard prisons holding more than 10,000 ISIS fighters and defend against Turkey's incursion.

Critics fear the SDF will abandon or release ISIS prisoners when it has to devote its resources to fighting Ankara.

The attacks also have distracted from NATO’s counter-ISIS campaign, though Joint Chiefs of Staff Chairman Gen. Mark Milley on Friday insisted that the fight against ISIS in Syria had not stopped.

The SDF “is still guarding prisoners in the area that have been detained over time,” he told reporters at the Pentagon while acknowledging the Turkish incursion “has had some effect” on the ISIS fight.

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The administration insists Turkey will be responsible for detaining ISIS fighters, but Brett McGurk, who resigned as Trump’s special envoy to the anti-ISIS coalition in December, warned Turkey “has neither the intent, desire, nor capacity” to manage ISIS detainees.

“Believing otherwise is a reckless gamble with our national security,” he tweeted.

US reputation damaged for future partnerships

In defending his decision to pull back U.S. troops, Trump has claimed he is fulfilling a campaign promise to halt “endless wars.”

But in leaving the SDF to fend for itself, lawmakers warn Trump has sent a chilling message to allies and potential U.S. partners who may want help in future conflicts.

The Trump administration "cut deal with [Turkish President Recep Tayyip Erdoğan] allowing him to wipe [the Kurds] out. Damage to our reputation & national interest will be extraordinary & long lasting," Sen. Marco Rubio Marco Antonio RubioGOP lawmakers distance themselves from Trump comments on transfer of power McConnell pushes back on Trump: 'There will be an orderly transition' Graham vows GOP will accept election results after Trump comments MORE (R-Fla.) wrote on Twitter on Wednesday.

The president also sparked backlash among lawmakers for downplaying the Kurds’ role in helping the U.S. fight against ISIS, tweeting that they "fought with us, but were paid massive amounts of money and equipment to do so."

Trump maintained during a rambling press conference Wednesday that the Kurds are merely "fighting for their land." He attempted to justify his stance based on the fact that Kurdish soldiers did not fight alongside Americans during World War II.

The Kurds "didn't help us in the Second World War, they didn't help us with Normandy as an example—they mention the names of different battles, they weren't there," Trump said.

Syrian Kurdish officials have accused the president of stabbing them in the back after 11,000 of their troops were killed in the battle against ISIS.

"Now we have been betrayed," Ilham Ahmed, co-chairman of the Syrian Democratic Council, the SDF's political arm, wrote in a Washington Post op-ed this week.

Defense Secretary Mark Esper Mark EsperOvernight Defense: Stopgap spending measure awaits Senate vote | Trump nominates former Nunes aide for intelligence community watchdog | Trump extends ban on racial discrimination training to contractors, military Overnight Defense: Pentagon redirects pandemic funding to defense contractors | US planning for full Afghanistan withdrawal by May | Anti-Trump GOP group puts ads in military papers Official: Pentagon has started 'prudent planning' for full Afghanistan withdrawal by May MORE insisted Friday that "we have not abandoned the Kurds" but said the U.S. was focused on protecting its own soldiers first.

Trump goes head-to-head with his own party

Some of the staunchest critics of Trump’s Syria move include numerous figures from his own party.

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The pushback came swiftly, with former U.N. Ambassador Nikki Haley Nimrata (Nikki) Haley'The soul' versus 'law and order' Author Ryan Girdusky: RNC worked best when highlighting 'regular people' as opposed to 'standard Republicans' GOP lobbyists pleasantly surprised by Republican convention MORE tweeting that leaving the Kurds “to die is a big mistake.”

Sen. Lindsey Graham Lindsey Olin GrahamLincoln Project mocks Lindsey Graham's fundraising lag with Sarah McLachlan-themed video The Hill's Morning Report - Sponsored by Facebook - Republicans lawmakers rebuke Trump on election Trump dumbfounds GOP with latest unforced error MORE (R-S.C.), a close Trump ally, called the decision a “disaster in the making,” adding that it “ensures [an] ISIS comeback” and “will be a stain on America’s honor.”

Graham, along with Sen. Chris Van Hollen Christopher (Chris) Van HollenCongress must finish work on popular conservation bill before time runs out Democrats fear Russia interference could spoil bid to retake Senate Mid-Atlantic states sue EPA over Chesapeake Bay pollution MORE (D-Md.), is looking to impose financial repercussions on Turkey.

House Republican Conference Chairwoman Liz Cheney Elizabeth (Liz) Lynn CheneyGOP lawmakers distance themselves from Trump comments on transfer of power Graham vows GOP will accept election results after Trump comments Liz Cheney promises peaceful transfer of power: 'Fundamental to the survival of our Republic' MORE (Wyo.) this coming week also plans to introduce legislation to implement sanctions on Turkey, an act that has already garnered more than two dozen GOP co-sponsors.

House Minority Leader Kevin McCarthy Kevin Owen McCarthyHouse to vote on resolution affirming peaceful transition of power Ginsburg becomes the first woman to lie in state in the Capitol McCarthy says there will be a peaceful transition if Biden wins MORE (R-Calif.), House Minority Whip Rep. Steve Scalise Stephen (Steve) Joseph ScaliseGinsburg becomes the first woman to lie in state in the Capitol House GOP slated to unveil agenda ahead of election House panel details 'serious' concerns around Florida, Georgia, Texas, Wisconsin elections MORE (R-La.) and House Armed Services Committee ranking member Mac Thornberry William (Mac) McClellan ThornberryOvernight Defense: Appeals court revives House lawsuit against military funding for border wall | Dems push for limits on transferring military gear to police | Lawmakers ask for IG probe into Pentagon's use of COVID-19 funds Democrats push to limit transfer of military-grade gear to police Trump payroll-tax deferral for federal workers sparks backlash MORE (R-Texas) are among the Republicans who have supported the legislation so far.

The Democratic chairman and ranking Republican on the House Foreign Affairs Committee said Friday they will also introduce legislation to slap sanctions on Turkey.

Washington's relationship with Ankara is further strained

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The relationship between the U.S. and Turkey has been tense over the last several years and was made all the worse in July after Ankara purchased a Russian air defense system.

The system is incompatible with other NATO systems and led the United States to remove Turkey from the F-35 joint strike fighter program, with U.S. national security personnel fearing the Russian system would allow the Kremlin to glean sensitive and protected information from the advanced fighter jet.

Esper on Friday said the United States is “greatly disappointed” by Turkey’s offensive in Syria and that it had damaged the already tense relationship between the two countries.

Making matters worse, U.S. Special Forces troops stationed in Syria came under artillery fire from Turkey late Friday, even as Milley earlier in the day said the Turkish military “is fully aware, down to explicit grid coordinate detail, of the locations of U.S. forces.”

The Pentagon maintained it “remains opposed” to the operation, especially “in areas where the Turks know U.S. forces are present,” and warned Turkey it may respond if U.S. troops are threatened.

“The U.S. demands that Turkey avoid actions that could result in immediate defensive action,” Navy Capt. Brook DeWalt said in a statement.

Rising tensions were underscored when the leaders of the House Foreign Relations panel signaled their support for legislation to slap sanctions on Turkey. The bipartisan bill would sanction Turkish officials and banks until the country ends its military operations in Syria.

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Treasury Secretary Steven Mnuchin on Friday also threatened “powerful sanctions” against Ankara and said the United States “can shut down the Turkish economy if we need to.”

Erdoğan said the same day, however, that Turkey “will not take a step back” from its offensive.

Russia, Iran empowered by move

Trump’s decision in northern Syria has left a potential power vacuum in the area, with security experts and former U.S. officials calling the move “a gift” to U.S. adversaries such as Russia and Iran.

“Trump tonight after one call with a foreign leader provided a gift to Russia, Iran, and ISIS,” McGurk said Monday on Twitter.

Moscow and Tehran have both inserted their militaries into Syria’s eight-year civil war, bolstering Syrian President Bashar Assad, while the United States has imposed sanctions on Russia for its support of the Assad government.

National security experts fear that Russian President Vladimir Putin Vladimir Vladimirovich PutinWatchdog confirms State Dept. canceled award for journalist who criticized Trump Former intelligence agency director Robert Cardillo speaks out against 'erratic' Trump Kremlin: Putin calls for reset between US and Russia on cyber relations before elections MORE, who has made no secret of extending the Kremlin’s influence into the Middle East, will use Trump’s move as an opportunity to gain more of a foothold in Syria.

Putin late this week called on foreign militaries to leave Syria as Turkey continued to wage its offensive while signaling that Russian forces would stay in the country until a new Syrian government tells Moscow it doesn't need any more help.

Russia already counts Turkey as a friend, with Moscow selling a missile defense system to Ankara earlier this year, drawing the ire of Washington.

Former CIA Deputy Director John McLaughlin slammed Trump for "impulsive and reckless instincts," calling his move this week “a disaster on multiple levels.”

“The kingmakers will be U.S. rivals Russia and Iran, working with a wandering U.S. ally, Turkey,” McLaughlin wrote Thursday.