Pakistan appointed a former information minister and human rights campaigner as its ambassador to the United States on Wednesday, moving quickly to fill a post left vacant after tension between the civilian government and military.

The prime minister is pleased to appoint Sherry Rehman as the new ambassador to the United States, said the spokesman for the prime minister's office, Akram Shaheedi.

Rehman is veteran member of President Asif Ali Zardari's Pakistan People's Party (PPP) and staunch proponent of civilian rule. Her appointment came as a surprise to many analysts who had expected someone closer to the military although they said she would be acceptable to the military.

It's an excellent choice, said retired general turned analyst Talat Masood. She has been on the security panel of the parliament. She understands security issues and at the same time she is on reasonably good terms with the military.

The same can not be said of the former ambassador to the United States, Husain Haqqani, who resigned on Tuesday, days after a Pakistani-American businessman accused him of being behind a memo that said the military was plotting a coup and appealed to the Pentagon to help ward it off.

Haqqani denied any connection with the memo.

The controversy has thrown a spotlight on the fundamental tension in Pakistani politics since the nation was founded in 1947 - competition for power between civilian politicians and military commanders.

The military has ruled the nuclear-armed South Asian country for more than half its history.

Political analyst Nasim Zehra said the president, the widower of assassinated former prime minister and pro-democracy leader Benazir Bhutto, appeared keen to ease the tension.

President Zardari is a man who is extremely smart and in a situation like this he obviously wants to reduce tension and the possibility of tension, said Zehra, host of a current affairs programme on Dunya TV.

DEATH THREATS

Rehman, a former journalist, was information minister for Zardari after the restoration of civilian rule following a 2008 election.

But she resigned in March 2009 over disagreements with Zardari on imposing media restrictions.

Rehman has been a strong advocate of women's and minority rights and faced death threats for her calls to reform the country's harsh blasphemy laws.

But she is also the author, through her role as president of the Jinnah Institute, of a report on Pakistan's foreign policy goals in Afghanistan, staking out views widely seen in Pakistan as dovetailing with those of the military establishment.

Military affairs analyst Ayesha Siddiqa said Rehman was acceptable to both sides of Pakistan's political divide.

If you send Sherry, you present the establishment's position and yet she has this human rights side and represents the PPP, Siddiqa said.

That will make her acceptable in Washington, where Haqqani was popular. Her human rights campaigning and liberal credentials would make the sacking of Haqqani less galling to his supporters there, she said.

Siddiqa said Rehman's appointment would have been negotiated between the government and the military leadership, who would have had to have approved the appointment.

Definitely this name would have come from the Kayani-Pasha team, she said, referring to army chief General Ashfaq Kayani and military intelligence chief Lieutenat-General Ahmad Shuja Pasha.

(Additional reporting by Augustine Anthony and Zeeshan Haider; Editing by Robert Birsel)