Pakistan's Prime Minister Yousuf Raza Gilani said Saturday 20 million people had been affected by the worst floods in the country's history as the UN confirmed the first cholera case.
Independence day celebrations were cancelled as floods continued to bring misery to millions and aid agencies warned of a "second wave" of deaths from disease.
"The floods affected some 20 million people, destroyed standing crops and food storages worth billions of dollars, causing colossal loss to national economy," Gilani said in a televised address. "I would appeal to the world community to extend a helping hand to fight this calamity."
The United Nations has appealed for 460 million dollars to deal with the immediate aftermath of the floods, but charities say the figure falls far short of what is needed.
UN Secretary General Ban Ki-moon was due to arrive in Pakistan on Sunday to discuss the relief effort and visit flood-hit areas.
"Outbreak of epidemics in the flood-hit areas is a serious threat, which can further compound the already grave situation," Gilani added, as the UN confirmed the country's first cholera case in Mingora, in the northwestern district of Swat.
Maurizio Giuliano, spokesman for the UN Office for Humanitarian Affairs, said at least 36,000 people were reportedly suffering from acute watery diarrhoea.
"We're not suggesting that everyone who has acute watery diarrhoea has cholera, but cholera is certainly a concern and that's why we're stepping up our efforts," he said.
Pakistan's chief meteorological official, Arif Mehmood, said no new wave of flooding was expected in the next couple of days.
But charities said relief for those affected by the worst natural disaster in Pakistan's history was lagging far behind what was needed.
"There are millions of people needing food, clean water and medical care and they need it right now," said Jacques de Maio, head of operations for South Asia at the International Committee of the Red Cross (ICRC).
"Clearly at this point in time the overall relief effort cannot keep pace with the overall scale of the emergency."
Humanitarian agencies in Pakistan were monitoring the risk of "a second wave of deaths induced by the floods in the shape of water-borne diseases", de Maio said.
Celebrations marking the anniversary Saturday of Pakistan's independence from British colonial rule were scrapped by President Asif Ali Zardari, who has come under fire for pressing on with a trip to Europe last week despite the emergency.
In his independence day message, Zardari said: "The best way to celebrate this day is to reach out to the victims of the natural disaster, heal their wounds and help them to help themselves."
"I salute the courage and heroism of flood victims and assure them that the government will do everything possible to alleviate their suffering."
However with up to two million people requiring shelter and six million depending on humanitarian assistance, troops distributed national flags among the people in the flood-hit northwestern town of Nowshera.
"We lost our houses and everything in the floods. We urgently need food and medicines and not the flags," Rasul Khan, 80, told AFP.
US Secretary of State Hillary Clinton telephoned Zardari to express solidarity, even as US security operations continued in the northwestern tribal belt. A missile fired from a US drone on a rebel compound in North Waziristan killed 13 militants on Saturday, according to local security officials.
"The people and government of the United States are with the people of Pakistan in these difficult times," an official government statement quoted Clinton as saying.
She also praised "the courage with which the people of Pakistan had braved the adversity".
The United Nations believes 1,600 people have died in the disaster, while Islamabad has confirmed 1,343 deaths.
Ban on Sunday was expected to "see for himself the flood-affected areas (and) demonstrate the support of the UN and the international community to the government and people of Pakistan," UN spokeswoman Ishrat Rizvi told AFP.
Meanwhile 90 percent of the 500,000 residents of Jacobabad left for safer ground after authorities warned that flood waters might deluge the southwestern city, provincial agriculture minister Jam Saifullah Dharejo told AFP.
