The resignation of Pakistan's ambassador to the United States, Hussain Haqqani, is an "internal issue" for Pakistan, the White House said while praising him as "a very close partner." Pakistan's government on Tuesday asked its US envoy to resign and ordered a probe into claims that he sought American help against the country's powerful military. Haqqani, a close aide of President Asif Ali Zardari, has played a key role in helping Pakistan's civilian government navigate turbulent relations with Washington which nosedived over the US raid that killed Osama bin Laden. Local media reports implicated Haqqani in a memo allegedly sent from Zardari to Admiral Mike Mullen, then America's top military officer, seeking to curtail Pakistan's military shortly after it was humiliated by the bin Laden killing. Zardari reportedly feared that the military might seize power in a bid to limit the hugely damaging fallout in Pakistan after Navy SEALs killed bin Laden in the garrison city of Abbottabad on May 2. "We, as we have said, see this very much as an internal issue relative to Pakistan," Deputy National Security Adviser for Strategic Communications Ben Rhodes told reporters. "He's been a very close partner, of course, with the United States and we've appreciated the work we've done with him. But at the same time we're certain that we'll be able to work with whomever the next Pakistani ambassador is." The alleged memo was revealed last month by American businessman Mansoor Ijaz. In an opinion piece in the UK's Financial Times on October 10, Ijaz wrote that a "senior Pakistani diplomat" telephoned him in May soon after bin Laden's death, urging him to deliver 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," he wrote. He said a memo was delivered to Mullen on May 10, offering that a "new national security team" would end relations between Pakistani intelligence and Afghan militants, namely the Taliban and its Haqqani faction. US Senate Foreign Relations Committee Chairman John Kerry, who has played a key role in often rocky relations between the two uneasy allies, said in a statement he was "sorry to learn" of Haqqani's resignation. "He was a strong advocate for his country and the Pakistani people. I respect the Pakistani government’s decision, but Ambassador Haqqani’s wisdom and insights will be missed here in Washington as we continue to work through the ups and downs of our relationship," said the Democratic lawmaker.