The letter, dated Thursday and addressed to the White House and U.S. legislators, also requests the United States take the lead in peace negotiations, The Hill reported Friday.
Aides to House and Senate leaders have not confirmed the letter's authenticity, and the White House has declined comment, the newspaper said.
The letter pledges to undertake democratic reforms and proposes the U.S. Congress send a fact-finding mission in support of a "special relationship" between Libya and the United States. It also appears to be an attempt to drive a wedge between the United States and its European allies, who have thus far taken a lead in the conflict.
The document, obtained by The Hill, seeks "a cease-fire, the funding of humanitarian relief and assistance in fostering and furthering accommodation between the parties within Libya that are at odds." It also singles out France, claiming the government of President Nicolas Sarkozy has taken the lead in Libya because it wants to "seize Libyan oil."
The three-page letter says "hostilities in Libya are an internal affair" and NATO's military actions are "inappropriate and illegal interference in what is essentially a Libyan civil war."
It also asserts Gadhafi has long sought "to establish a special relationship with the United States of America based on mutual respect and mutual benefit. We were the first country to issue an arrest warrant for [Osama] bin Laden and the first country that stood in solidarity with the United States regarding the events of 9/11 and this horrific terrorist attack on the Twin Towers."
In April Gadhafi sent a letter to President Barack Obama calling for an end to NATO airstrikes.