Mullen never met Pakistani American businessman Mansoor Ijaz, who has alleged that Pakistan's ambassador to the US, Hussain Haqqani, asked for assistance in getting a message from Pakistan President Asif Ali Zardari to the then top US military leader, Pentagon spokesman, Captain John Kirby told reporters Monday.

Ijaz has alleged that Zardari feared a military takeover following the US raid that killed Osama bin Laden in Pakistan in May and sought Mullen's help in preventing a coup. Asserting that the admiral did not take the alleged secret memorandum seriously as it was "not signed" and there was no indication that it was coming from the Pakistan President, Kirby said adding the contents of the said letter were not reliable and authenticated.

Asked about a Pakistani media report that former National Security Advisor Gen James Jones had admitted to carrying the memo to Mullen, he said: "I am not going to speak to Gen Jones participation in it and if he is speaking that is certainly his account."

"I have said this before and am saying again today. Nothing about that letter had the imprimatur on the Pakistani Government," the Pentagon spokesman said. "It was not signed. And the contents of it Admiral Mullen did not find credible. So he took no action on it."

"He (Mullen) knew who the third party was who was giving it (this memo) to him. He does not know Mr Ijaz. He never communicated with Mr Ijaz. He did not know that Ijaz was the author of this alleged memo.

"He simply got the memo from a third party, read it and decided to do nothing with it because he did not find it at all credible," Kirby said. Asked about Haqqani's alleged role, State Department spokesperson Victoria Nuland said as far as they knew the Ambassador "is home on consultation."

"We always expect that Pakistan's leaders will act in accordance with Pakistan's constitution and in a manner respectful of its democratic institutions. So beyond that, I don't have any specific comments on this issue," she added.