Democrat Gabbard, a major in the Army National Guard, told CNN that she met with Assad during a secret "fact-finding" trip she took to the country.
"My reason for going to visit Syria was really because of the suffering of the Syrian people that has been weighing heavily on my heart. I wanted to see if there was in some small way that I could express the love and the 'aloha' -- a Hawaiian word used when greeting -- and the care that the American people have for the people of Syria and to see firsthand what was happening there," she told the channel.
"But when given the opportunity, I felt it was important to take it," Congresswoman Gabbard, who supported Vermont Senator Bernie Sanders during the last year's primaries, said.
"Whatever you think about President Assad, the fact is that he is the president of Syria," Gabbard told CNN, adding that there is no possibility for a viable peace agreement in Syria unless Assad is part of the conversation.
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Former President Barack Obama has said repeatedly that the autocrat should not be part of Syria's future, though Assad is currently more entrenched in power after receiving military support from Russia.
She said that the "moderate" rebels supported by the US are no different from extremists in the region such as al-Qaeda and the ISIS, and has introduced legislation to stop US government funding going towards those who may indirectly use the money to help terrorist organisation.
Trump, during debates with Hillary Clinton, had said that the US does not know who the anti-Assad rebels really are, and praised the Syrian president for fighting ISIS.