Turkish President Recep Tayyip Erdogan sparked tensions during his US visit when he showed Republican senators an anti-Kurdish video, US media say.
On Wednesday Mr Erdogan played the video on an iPad during a White House meeting with President Trump and the lawmakers who vocally back the Kurds.
President Donald Trump mostly observed the interaction, sources told US media.
Mr Trump has been widely criticised in the US for his decision to withdraw troops from Syria’s border region.
The Kurdish-led Syrian Democratic Forces (SDF) – which are supported by the US – played a leading role in the fight against Islamic State (IS) militants.
The senators involved in Wednesday’s meeting were Lindsey Graham, Ted Cruz, Rick Scott, Joni Ernst, and Jim Risch.
All five have sharply criticised Mr Erdogan’s October move against Kurdish forces in Syria following Mr Trump’s announcement to pull US troops.
Turkey regards the Kurdish fighters as terrorists and is seeking to turn the area into a “safe zone” for resettling the Syrian refugees currently in Turkey.
Mr Erdogan reportedly believed he might change the senators’ views on the Kurds by showing them the short film, but instead received pushback from the entire group.
After viewing the film, Mr Graham asked Mr Erdogan if he wanted him “to go get the Kurds to make one about what you’ve done”, prompting a heated discussion, a source present during the meeting told the Axios news website, which first reported the incident.
Mr Trump only occasionally intervened in the conversation as the senators took turns debating Mr Erdogan.
The US president said during a news conference on Wednesday he was a “big fan” of Mr Erdogan. He has previously said that the Kurds are “not angels”.
President Trump had invited the lawmakers to speak to Mr Erdogan to try to persuade him to avoid buying Russian military equipment, administration sources told US media.
Turkey has been threatened with sanctions if it continues to deploy Russian defence systems.
The senators have said they will not allow Turkey to purchase US fighter jets if Mr Erdogan continues to procure equipment from Russia.
Following the meeting, Mr Cruz released a statement saying he has always viewed Turkey as “a deeply problematic ally, but an ally nonetheless”.
“While our alliance with Turkey is important to maintaining US national security interests, Turkey’s assault against our Kurdish allies, who have a long history of standing with America against our enemies, is absolutely unacceptable.”
Mr Graham “forcefully” rejected the “Turkish narrative that they have done more to destroy Isis”, he told Axios, using an alternative name for IS.
“I let Turkey know that 10,000 SDF fighters, mostly Kurds, suffered, died or injured, in the fight against Isis, and America will not forget that and will not abandon them.”