Pakistan's ambassador to the United States returned to Islamabad Sunday to explain a controversial memo appealing to the United States to help rein in the country's powerful military.

Ambassador Husain Haqqani has been the focus of a political dispute over the letter sent in May to Admiral Mike Mullen, the top U.S. military official at the time.

The memo called for U.S. help in preventing a military coup in Pakistan following the American raid that killed former al-Qaida leader Osama bin Laden. It was sent by Mansoor Ijaz, a U.S. citizen of Pakistani origin, allegedly at the request of Haqqani.

A close ally of Pakistani President Asif Ali Zardari, Haqqani has denied any connection with the memo and offered to resign over the dispute. He is set to meet with Mr. Zardari and other Pakistani leaders during his visit to discuss the scandal.