A former Republican congressman has arrived in Libya on a mission to meet Col Muammar Gaddafi and ask him to step down from power.
Curt Weldon, who met the Libyan leader in 2004, says it is a private visit, with the knowledge of the White House.
Mr Weldon also reportedly intends to ask Col Gaddafi to allow democratic elections and says one of his sons could help form a new government.
Meanwhile, President Barack Obama has received a letter from Col Gaddafi.
White House press secretary Jay Carney confirmed that President Obama received the letter from Col Gaddafi, which was sent to the US state department and then forwarded to the White House.
In the three-page letter, Col Gaddafi asked Mr Obama to end the Nato-led air campaign and called the conflict in his country an "unjust war against a small people of a developing country", the Associated Press reported.
"You are a man who has enough courage to annul a wrong and mistaken action," Col Gaddafi said, adding that he is sure Mr Obama is "able to shoulder the responsibility for that".
Col Gaddafi also reportedly said Libya has been damaged more morally than physically by Nato forces.
State television in Tripoli says the Libyan leader was marking the withdrawal of the US from what it called the "hostile, colonial alliance".
That is a reference to the reduced American role in the Nato operation.
The visit by Mr Weldon, who represented Pennsylvania from 1987 to 2007 and was part of a Congressional delegation to Libya in 2004, comes at the invitation of the Gaddafi government but with the backing of the White House and members of Congress, the former congressman wrote in a New York Times article.
"Our purpose is to meet with Colonel Qaddafi today and persuade him to step aside," he wrote, using an alternative spelling of the Libyan leader's name.
Mr Weldon said the US has failed to engage with leaders in Libya aside from Col Gaddafi and failed to encourage peaceful democratic reforms in the past several years.
"There is no question that America should play a critical role in helping the Libyans build a new government," Mr Weldon said.
Mr Weldon added that it was important to engage in a dialogue with Col Gaddafi because he has met him "enough times to know that it will be very hard to simply bomb him into submission".
Mr Weldon also suggested that Mr Gaddafi's son, Saif, could play a constructive role in developing a new framework for government, together with leading members of the Libyan opposition.
White House officials declined to comment on the visit.
Protecting rebel forces
News of the visit emerged as the International Criminal Court reported that the Libyan government had planned to crush protests by killing civilians even before the uprising in Libya broke out.
The chief prosecutor said the plans had been a reaction to street protests that led to the fall of the Tunisian regime.
Rebel opposition forces in Libya on Wednesday accused Nato forces of failing to protect Misrata city.
Rebel commander Gen Abdul Fattah Younis told reporters in the de facto rebel capital Benghazi that Nato "is letting the people of Misrata die every day".
But Nato deputy spokeswoman Carmen Romero told the AFP news agency that "Misrata is our number one priority".
Nato says international air strikes, aimed at protecting civilians and enforcing a no-fly zone, have reduced Col Gaddafi's military capabilities by nearly a third, but his forces have deliberately moved weaponry into civilian areas to hamper air strikes.
The revolt against Col Gaddafi's rule began nearly two months ago.