Ambassador Hussain Haqqani told The Washington Post he had written to Pakistani President Asif Ali Zardari, "I do not want to be a distraction from the major challenges facing our country and our government."
Haqqani has been accused of taking part in a memo asking for U.S. intervention to stop a Pakistani military coup following the May killing of al-Qaida leader Osama bin Laden by U.S. forces inside his compound in Pakistan.
Although the Pakistani government had no immediate comment, the Post said Haqqani has been asked to come home for consultations.
Separately, in a Washington-datelined story in Pakistan's Dawn newspaper, a senior diplomatic source, was quoted as saying: "We cannot call it a resignation. He [Haqqani] has sent a letter to prove that he is not guilty."
The Dawn report said the ambassador is believed to have written that he was not responsible for the letter that allegedly sought U.S. support for sacking Pakistani army and intelligence chiefs, and offered to resign if proven guilty.
The Post said in a Financial Times commentary last month, Mansoor Ijaz, a Pakistani American, said an unnamed Pakistani diplomat had enlisted him to help compose a message.
Ijaz said the message was to be transmitted, through a conduit, from Zardari to Adm. Mike Mullen, then chairman of the U.S. Joint Chiefs of Staff, saying "needed an American fist on his army chief's desk to end any misguided notions of a coup -- and fast."
Ijaz was quoted as saying after Pakistani Army Chief Ashfaq Kayani and the country's intelligence head, Lt. Gen. Ahmed Shuja Pasha, had been replaced, a new Pakistani security team would eliminate the intelligence agency, which is seen as being tied to the Pakistan-based Taliban and the dreaded Haqqani network.
The Post said Ambassador Haqqani in his interview said he had been in contact with Ijaz "at various times during the last 10 years," but that he "did not draft or deliver the memo and I had no authority to conceive or authorize such a memo."