Flooding has killed more than 1,500 people, according to the United Nations, and affected more than 17 million. Hundreds of thousands of homes have been destroyed, and more than 1.7m acres of farmland are underwater.

"I don't think Pakistan will ever fully recover, but we will move on," Zardari said.

Sindh threatened

The waters are once again threatening southern Sindh province, where the Indus river has reached dangerously high levels at the Kotri barrage.

SPECIAL COVERAGE

Flooding has already submerged a number of villages in Thatta and Larkana districts in Sindh. Workers have frantically piled sandbags and rebuilt levees, and hundreds of thousands of people have been evacuated from the area.

Authorities estimated that 90 per cent of the 350,000 residents of the city of Shahad Kot have already fled.

More than 18km of new levees have already been built in Shahad Kot and nearby Qambar, but authorities worry that the rising floodwaters may top those barriers. The floods have been racing south down the Indus for several days.

'Epidemic diseases'

Millions of people displaced by the floods have yet to receive any aid, and the UN said on Tuesday that more than 800,000 people have been cut off, reachable only by air.

Pakistani officials and aid organisations continue to warn of the threat of a disease epidemic. The UN says more than 3.5m children are at risk of waterborne diseases. And the flooding has ravaged Pakistan's medical system: More than 200 hospitals and clinics are damaged.

Yousuf Raza Gilani, the Pakistani prime minister, warned on Tuesday that the country should prepare for an epidemic.

"As human misery continues to mount, we are seriously concerned with the spread of epidemic diseases," he said during a visit to a makeshift health clinic.