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The United States may be about to lose its greatest advocate among the Pakistanis -- the Pakistani ambassador to the U.S. -- who has been critical to conveying the need for cooperation from one of America's most important allies in eradicating Islamic militants.

Husain Haqqani has reportedly offered his resignation after being implicated in a scandal surrounding a memo given to the U.S. military on the behalf of Pakistan's president. The document requests America help him remove the leadership of his country's all-powerful military.

The memo was passed to the then-U.S. Chairman of the Joint Chiefs of Staff Adm. Mike Mullen in the days after Usama Bin Laden was killed on May 2 in northern Pakistan.

Its existence was revealed last month in a Financial Times opinion column by Pakistani businessman Mansoor Ijaz. Ijaz claims he was asked by a senior Pakistani diplomat for assistance in passing the note to Mullen from Pakistani President Asif Ali Zardari.

Ijaz claimed that Zardari feared a military coup in the wake of bin Laden's elimination, which humiliated the Pakistani army so much that it threatened its four-decade de facto control of the country.

Since that raid, when tensions between Washington and Islamabad were already strained, the relationship has slumped so low that a former ambassador has described it as a "bad marriage where divorce is impossible."

The memo controversy comes as Congress debates how much financial support the United States should continue giving Pakistan, which has received more than $25 billion in mostly military assistance since Sept. 11, 2001. Despite the income, Islamabad has struggled to prevent militants on its soil from targeting NATO troops in neighboring Afghanistan.

The memo itself has yet to be made public but people in Islamabad close to Ijaz say Haqqani held an exchange of encrypted Blackberry messages, emails and phone calls with Ijaz discussing how the letter should be drafted, approved by officials in Pakistan, and then passed to the U.S. military.

The businessman has since been leaking excerpts from those conversations to Pakistani media.

The transcripts, which have not independently been confirmed, indicate that Ijaz wrote the original draft and that the senior Pakistan official edited it before it was given "approval by the boss" in Islamabad.

According to the transcript, the senior official says via email:  "With final agreed draft of memorandum, pending one final approval from Pakistani official to confirm agreement on content and agreement to go ahead with delivery to Admiral Mullen"

The memo was then allegedly handed to senior U.S. officials on American soil on May 11 at a meeting with Pakistani counterparts.

Mullen's former spokesman Cpt. John Kirby said Thursday that Mullen has no recollection of the memo and no relationship with Ijaz, but upon inquiry was reminded of the memo from someone who had knowledge of it.

Kirby said neither the contents of the memo nor the proof of its existence altered or affected in any way the manner in which Mullen conducted himself in his relationship with Pakistani Army Chief Gen. Ashfaq Parvez Kayani and the Pakistani government. He added that Mullen did not find the memo at all credible and took no note of it then or later. Therefore, he did not discuss its contents with anyone.

Ijaz's revelations in The Financial Times erupted into controversy in Pakistan last month. There were strong public rebuffs by the government and the military.

The transcript includes these exchanges made over BlackBerry's encrypted Messenger service:

10/28/2011 21:37 [PAK OFFICIAL]: You have given hardliners in Pak Mil reason to argue there was an effort to get US to conspire against Pak Mil

10/28/2011 21:40 Mansoor IJAZ: But from my point of view, if there was a real threat, as you stated at the time, it is clear you were trying to save a democratic structure from those hawks

10/28/2011 21:41 [PAK OFFICIAL]: You get to write the book on how you changed US-Pak dynamic and won the war in A'tan (w/ some help from a Paki nerd) :D

10/28/2011 21:42 Mansoor IJAZ: I was happy to get the message in the back door because it served American interests to preserve the democratic civilian setup and the offers made, if achieved, were very much congruent with American objectives in the region

10/28/2011 21:42 [PAK OFFICIAL]: True that, friend. But you know premature revelation ain't good

10/28/2011 21:43 Mansoor IJAZ: As far as I can see, we did right. Unless there is something I don't see here. But then I'm sorta dumb from down on the farm where them hillbillies live

10/28/2011 21:43 [PAK OFFICIAL]: Hey! Don't run down hillbillies

Haqqani is a heavily pro-America Pakistani, with strong ties to Washington and who has held his post since 2008. He was exiled in 1999 following criticisms against the government of then-President Pervez Musharraf. His tongue-in-cheek Tweet feed is filled with criticisms of his home country and overt expressions of his love for the United States.

A source who spoke to Fox News says Haqqani has been recalled to Islamabad to explain his role in the scandal to military leadership but the Pakistanis have tried to publicly play it down by saying he is to return for a "routine briefing on U.S./Pak relations."

The Pakistani embassy in Washington D.C., did not respond to an interview request. But Haqqani tweeted Wednesday, "How does envoy deflect Pakistani anger at US? One tweet at a time."

A business contact in Islamabad with whom Ijaz has shared close details of the memo but who did not want to be identified for this report due to the sensitivity of the matter, told Fox News that Haqqani "has done a good job for Zardari."

"He's ingrained in the U.S. system. The Pakistan military have no idea how the U.S. system works, nor America's high level of accountability. No soldier has accountability here" -- a reference to the fact that Pakistan has never explained how it was possible bin Laden was hiding for years just 40 miles from the its capital.

Haqqani is not expected to return home before the weekend. His embassy said his priority is to lobby ahead of Thursday's congressional debate on appropriations to Pakistan.