The revelation by a US Democratic congresswoman that she met Syrian President Bashar al-Assad has drawn criticism from lawmakers.
Tulsi Gabbard said on Wednesday she had talked to Mr Assad during a recent trip to Syria, and was “ready meet with anyone if there’s a chance it can help bring about an end to this war.”
Democratic Congress leaders had not been notified of the trip in advance.
Republican congressman Adam Kinzinger called it “a shame and a disgrace”.
“In no way should any member of Congress, should any government official, ever travel to meet with a guy that has killed 500,000 people and 50,000 children,” said Mr Kinzinger who, like Ms Gabbard, is an Iraq War veteran.
The trip left experts wondering if Ms Gabbard, a representative from Hawaii, had violated legislation prohibiting unauthorised individuals from speaking to governments in dispute with the US.
The US has accused the Syrian government of deliberately targeting civilians and the two countries have no formal diplomatic relations.
“I have no knowledge of the trip,” Nancy Pelosi, the top House Democrat, said on Thursday. “She hasn’t reported or brought anything to our office as far as I know.”
In an interview with CNN on Thursday, Ms Gabbard said that she had not initially planned to meet Mr Assad during her visit.
“When the opportunity arose to meet with him, I did so, because I felt it’s important that if we profess to truly care about the Syrian people, about their suffering, then we’ve got to be able to meet with anyone that we need to if there is a possibility that we could achieve peace,” she said.
After her week-long visit to Syria, Ms Gabbard submitted the “Stop Arming Terrorists” bill, which is designed to halt US support for Syrian rebel groups.
In a statement on Wednesday she urged the US to “end our war to overthrow the Syrian government and focus our attention on defeating al-Qaeda” and the so-called Islamic State.
Under former President Barack Obama, Mr Assad was repeatedly referred to as a “war criminal” by US lawmakers.