Pakistan's powerful army is fed up with unpopular President Asif Ali Zardari and wants him out of office, but through legal means and without a repeat of the coups that are a hallmark of the country's 64 years of independence, military sources said.

Tensions are rising between Pakistan's civilian leaders and its generals over a memo that accused the army of plotting a coup after the U.S. raid that killed Osama bin Laden in May.

"Who isn't fed up with Zardari? It's not just the opposition and the man on the street but people within the government too," said one military source who asked not to be named.

"But there has to be a proper way. No action is being planned by the army. Even if we tried, it would be very unpopular and not just with the government and the opposition but most Pakistanis too."

The Pakistani military spokesman declined comment.

General Ashfaq Kayani has pledged to keep the military out of Pakistani politics since taking over as army chief in 2007.

Any coup - Pakistan has had three since independence in 1947 -- could further tarnish the military's public image which has already taken a battering after the bin Laden operation, widely seen in Pakistan as a violation of sovereignty.

But the army remains the arbiter of power and analysts say it has plenty of ways to pressure Zardari to step down, especially if a link is established between him and the memo, which sought the Pentagon's help in averting a feared coup.

Businessman Mansoor Ijaz, writing in a column in the Financial Times on October 10, said a senior Pakistani diplomat had asked that a memo be delivered to the Pentagon with a plea for U.S. help to stave off a military coup in the days after the raid that killed al Qaeda leader Osama bin Laden in May.

Ijaz later identified the diplomat as Pakistan's ambassador to Washington, Husain Haqqani, who denied involvement but resigned over the controversy. No evidence has emerged that the military was plotting a coup and the Pentagon at the time dismissed the memo as not credible.

Friction between Pakistan's civilian government and military have bedeviled the nuclear-armed South Asian country for almost its entire existence, with the military ruling for more than half its 64-year history after a series of coups.

In the past the army has asked Pakistani civilian leaders to resign and influenced judicial proceedings against them.

Haqqani's resignation was seen by many analysts as further weakening the civilian government, which is already beset by allegations of corruption and incompetence in the face of many challenges, including a weak economy and a Taliban insurgency.

MEMOGATE

Zardari returned to Pakistan this week from medical treatment in Dubai that raised speculation he would resign under pressure from the military over what has been dubbed "memogate."

Although his position is largely ceremonial, he wields considerable influence as leader of the ruling party and his forced departure would be a humiliation for the civilian leadership and could throw the country into turmoil.

One of the military sources suggested that no direct action would be needed against the government because it had already made so many mistakes.

"If the government is digging its own grave, we are not going to look for spades," the source said.

The military has reasserted itself after a November 26 NATO cross-border air attack killed 24 Pakistani soldiers and the memo has also given it political ammunition.

In a statement submitted to the Supreme Court, which is looking into a petition demanding an inquiry into who may have been behind the memo, Kayani said it was a serious matter which required an investigation.

"We want anyone involved, be they in government or elsewhere, to be punished. But it is not for us to do anything. If the army moves to do anything it would have national as well as international repercussions," said another military source.

"So that is not likely. Anything that has to be done has to be done by the Supreme Court."

Officials from Zardari's ruling party have played down friction with the military and say they don't fear a coup.

But they fear that some judges in the increasingly aggressive Supreme Court dislike Zardari and could move against him.

"I am not bothered about the army. I think they are acting very sensibly and would not derail the system at the moment," a senior ruling party leader told Reuters.

"The worry probably would be what the Supreme Court does. They look in a mood to manipulate things."

The government's anxiety over memogate was highlighted in comments made by Prime Minister Yusuf Raza Gilani on Thursday.

"Let me make clear to you today that there are intrigues, conspiracies afoot to pack up the elected government," he said in a speech at the National Art Gallery.