Pakistan's ambassador to the United States, Hussain Haqqani, has offered to resign after being summoned to Islamabad to explain himself over reports that he sought Washington's help against the Pakistani army on behalf of President Asif Ali Zardari.

Haqqani, a close aide of Zardari, has played a key role in helping Pakistan's civilian government navigate turbulent relations with the US, which nose-dived after the raid that killed Osama bin Laden in Pakistan in May.

Local media reports in Pakistan on Thursday implicated Haqqani in a memo allegedly sent from Zardari to Admiral Mike Mullen, then the top military officer in the US, that sought to curtail Pakistan's military after it was humiliated by the bin Laden killing.

Zardari reportedly feared that the military might seize power as one way to limit the hugely damaging fallout in Pakistan after US special forces killed bin Laden in the garrison city of Abbottabad on May 2.

In remarks to CNN on Wednesday, Haqqani denied writing the memo but confirmed he had offered to resign if it would end "the vilification against the democratic government of Pakistan".

"No memo of the kind being discussed in the media was drafted or delivered by me," Haqqani said. "I have not been named so far as having done anything wrong by anyone except through innuendo."

He said he was being targeted by part of ongoing "smear campaigns".

Rehman Malik, the Pakistani interior minister, accused the media of hounding Zardari over the memo, the existence of which was revealed in an op-ed last month by US businessman Mansoor Ijaz. Malik said that Haqqani would explain his role.

"Yes, he [Haqqani] had been summoned by the president," Malik told reporters outside parliament in Islamabad.

"He has already offered his resignation to the president, saying hype has been created and he was ready to resign in the national interest. If he has done something beyond his mandate, he can come and explain it."

Al Jazeera's Kamal Hyder, reporting from Islamabad, said that there was "an understanding that the memo was sanctioned with the highest level of the political government."

Writing in the UK's Financial Times on October 10, Ijaz said a "senior Pakistani diplomat" telephoned him in May, saying that Zardari wanted to get a message to the White House bypassing Pakistan's military and intelligence chiefs.

"The president feared a military takeover was imminent" and "needed an American fist on his army chief's desk to end any misguided notions of a coup, and fast," said the article published on the opinion pages.

Ijaz said a memo was delivered to Mullen on May 10 and that it suggested a "new national security team" in Pakistan would end troublesome relations between Pakistani intelligence and Afghan fighters, namely the Taliban and its Haqqani faction.