"We continue to strongly advise all USA citizens not to travel to Syria", Pompeo said.
Shibly told BuzzFeed News on Wednesday that she was born in the USA state of New Jersey.
"To say that I regret my past words, any pain that I caused my family and any concerns I would cause my country would be hard for me to really express properly", she said in a handwritten note to her lawyer.
"I personally called them, I said, 'Listen we know where she is and she's ready to speak with you".
Hassan Shibly made the comments about Hoda Muthana on "America's Newsroom" a day after President Trump and Secretary of State Mike Pompeo vowed to keep Muthana out of the country and denied she was a U.S citizen. Her lawyer is challenging that claim. She said she feels remorse and sorrow and regret, and begged to return home.
"She's an American. Americans break the law", Mr Shibly said.
Her lawyers say she could be useful to the government and the Federal Bureau of Investigation because she is familiar with the terror group.
"ISIS bride" Hoda Muthana, who has been asking to return to the United States, is not an American citizen, Secretary of State Mike Pompeo said in a statement on Wednesday, contrary to her family lawyer's assertion.
Pompeo says Hoda Muthana does not have a USA passport or any legal basis to enter the country. "I would tell [US officials] please forgive me for being so ignorant", she said, "and I was really young and ignorant and I was 19 when I chose to leave".More news: Two policemen killed in Cairo explosion: interior ministry
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Muthana was born in the United States to parents from Yemen who became naturalized American citizens, according to the Counter Extremism Project at George Washington University, which has identified 64 Americans who went to join IS in Syria or Iraq.
After her second husband was also killed she married a third IS fighter but she "became disenchanted with the marriage", and chose to escape, the lawyer said.
Muthana's father resigned from his post as a Yemeni diplomat months prior to Muthana being born, but Shibly says that her father's prior position is why the United States is attempting to say she never had citizenship.
Just this weekend, Trump took to Twitter to chastise European allies that have not taken back hundreds of Islamic State prisoners caught in Syria, where Trump plans to withdraw U.S. troops.
The only significant exception is children of accredited foreign diplomats, as the 14th Amendment provides citizenship to everyone "subject to the jurisdiction" of the United States. Britain recently revoked the citizenship of Shamina Begum, who similarly traveled to Syria and wants to return to her country of birth.
"They're saying her father was a diplomat when she was born, and therefore she was not entitled to citizenship".
"In my quiet moments, in between bombings, starvation, cold and fear I would look at my lovely little boy and know that I didn't belong here and neither did he", she said in the handwritten letter, a copy of which was provided by Shibly. "She's not coming back", he said.
"During my years in Syria I would see and experience a way of life and the awful effects of war which changed me". Americans break the law.
During her time in Raqqa, Syria she has been married three times, given birth to a son and been active on the now-deleted Umm Jihad Twitter handle.