Political tensions forced Zardari to transfer authority over Pakistan's nuclear weapons to the prime minister last week. The move was symbolic because Pakistan's military remains in control of the arsenal.

But it highlights the deeply unpopular Zardari's scramble to pacify the opposition and head off calls for his resignation.

The turmoil raises the possibility, although remote, that another civilian government will fail to serve a full term in a nation ruled by the military for over half of its 62-year history.

Zardari's controversial policies - such as signing a conditional US aid package - have enraged the all-powerful military and ordinary Pakistanis.

'He is not in threat of being locked out let's say in four weeks or six weeks. But he is under a lot of pressure, a lot of criticism because of the way he conducted himself in the past,' said political analyst Hasan Askari Rizvi .

'If he amends his ways then I think he may continue until some new crisis emerges.'

The opposition wants Zardari to give up sweeping powers inherited from his predecessor Gen. Pervez Musharraf, whose cooperation with the United States in the fight against terrorism and tussle with the judiciary ultimately led to his demise.

An amnesty paved the way for Zardari's wife Benazir Bhutto to return from self-imposed exile in October 2007. She was assassinated just over two months later, leaving Zardari to lead her party to victory in general elections in February 2008 and then become president after Musharraf resigned in August.

Zardari's downfall would complicate US efforts to secure more support for its battle against the Taliban in Afghanistan. Failure there could damage President Barack Obama's presidency.

BACKED INTO A CORNER

While few expect Zardari's imminent fall, Pakistani commentators and media suggest it's only a matter of time.

Pakistan's domestic troubles come at a critical time for the strategic region. Obama is expected to announce on Tuesday he will deploy 30,000 more US troops in Afghanistan.

A surge would create more difficulties for Zardari, who lacks Bhutto's charisma and is so seldom seen in public that one newspaper recently called him 'the invisible President.'

Officials fear it would push Taliban fighters into Pakistan, which is already struggling against militants who have killed hundreds in bombings since October in reaction to an offensive.

British Prime Minister Gordon Brown urged Zardari over the weekend to take tougher action to track down Osama bin Laden and crack down harder on the Taliban.

Pakistan's military runs the campaign against militants. So Zardari would be taking big risks if he bows to Western pressure and tries to take command of security policies.

Political analysts say, that for now, the military is only interested in keeping Zardari in line.

'They can apply pressure by making one or two statements here and there and the opposition will get encouraged, the opposition will get enough signals to build pressure on him,' said Rizvi.

'The only thing the military wants is that any high-policy security matter should be settled in consultation with them, rather than unilateral decision making.'

ARRAY OF PROBLEMS

Zardari faces an array of other problems. Public anger is growing over rising food prices some blame on influential businessmen and politicians. The economy is in virtual recession. Security concerns have put off investors.

But he may only have time to fight for his survival.

After Zardari spent 11 years in jail in Pakistan on corruption and murder charges - though never convicted - he is left open to old allegations resurfacing, now that the amnesty has elapsed.

Zardari cannot be prosecuted because of presidential immunity, but a revival of graft cases against officials close to him could deal a lethal political blow.

If his position becomes untenable, Washington may look around for another ally, hoping to secure political stability in Pakistan and increase the chances of defeating the Taliban.

An obvious choice would be Pakistan's most popular politician and Zardari's main rival Nawaz Sharif, the former prime minister ousted by Musharraf in a bloodless coup in 1999.

So far, Sharif seems hesitant to capitalize on Zardari's misfortunes, perhaps fearful of a full-blown political crisis during sensitive times.

Asad Durrani, former director general of Pakistan's ISI spy agency, believes a Zardari exit would help.

'It would be a good beginning. Because he is so controversial. He takes up so much time of the government, of the media, of civil society,' said Durrani.

Some Pakistanis, like plumber Mohammad Sajid, say the country may as well keep Zardari.

'If Zardari goes, then the new leader will be worse, it's our experience. Therefore, I think may Allah guide him to improve his performance and he completes his five years,' he said. – Reuters