KARACHI: Pakistan's Ambassador to the United States Husain Haqqani has departed for Islamabad, DawnNews reported.

Haqqani is expected to answer allegations he wrote an explosive memo that asked for Washington's help in reining in the Pakistani military.

Pakistan's civilian government has been facing a crisis following a claim by Mansoor Ijaz, a US citizen of Pakistani origin, that he delivered a memo to then-US military chief Adm. Mike Mullen a week after the US raid killed al-Qaeda leader Osama bin Laden in Abbottabad.

The memo allegedly requests US help in installing a ''new security team'' in Islamabad friendly to Washington.

Ijaz says that the ambassador, Husain Haqqani, was behind the memo.

Haqqani, who denies he was behind the memo, tweeted on Saturday he was heading to the ''motherland''. Officials confirmed his return.

Haqqani also met with US special envoy for Afghanistan and Pakistan Marc Grossman before departing for Islamabad.