Pakistan has a new ambassador to the United States following a controversy about a memo appealing for U.S. help in reining in Pakistan's powerful military.

Officials said Prime Minister Yousuf Raza Gilani appointed former information minister Sherry Rehman to the post on Wednesday, a day after former ambassador Hussain Haqqani resigned.

Haqqani has denied calling for U.S. help in preventing a military coup in Pakistan following the American raid that killed former al-Qaida leader Osama bin Laden. The memo was sent in May to Admiral Mike Mullen, the top U.S. military officer at the time.

The new ambassador has been a lawmaker for the ruling Pakistan People's Party and has ties to the United States, where she studied politics and foreign relations in the 1980s at Smith College.

Rehman is an advocate for minority rights, and has faced threats for her challenges to the country's blasphemy laws.

Rehman also serves as chairman of the Jinnah Institute, a think tank and advocacy group in Pakistan.

Haqqani had been the ambassador to the United States since 2008, and was well-regarded in Washington. He is a close ally of Pakistani President Asif Ali Zardari.

Mr. Gilani's spokesman said Tuesday that Haqqani was asked to step down to allow a proper investigation.

Pakistani-American businessman Mansoor Ijaz described the memo in an opinion piece published last month in the Financial Times newspaper.

In return for U.S. help in preventing a military coup in Pakistan, the memo said a new national security team would conduct a full inquiry into allegations that Pakistan harbored bin Laden. The new team would also hand over top al-Qaida members and ensure that Pakistan's military spy agency cuts ties to the Taliban, the Haqqani network and other groups.

Ambassador Haqqani said Tuesday that he was resigning to bring closure to the “meaningless controversy threatening our fledging democracy.” He added on Twitter that he has “much to contribute to building a new Pakistan free of bigotry and intolerance.”