Pakistani Prime Minister Yusuf Raza Gilani cancelled his attendance at next week's UN General Assembly session in New York, saying Friday he needed to co-ordinate flood relief efforts at home.
Monsoon rains have flooded large parts of the southern Sindh province over the last six weeks, leaving more than 200,000 people homeless.
Pakistan's leaders came under criticism last year for failing to deal with floods that affected more than a quarter of the country's territory.
Local authorities, the United Nations, and foreign and local aid groups are distributing water, medicine and food, while the army is rescuing people from communities trapped by the waters. But many thousands have received little or no help and are living in the open under rainy skies or scorching sun.
Gilani said Pakistan's foreign minister would address the Assembly in his place.
Last year's floods affected most areas of the country, including Sindh, and prompted a large international relief effort.
The U.S. military, keen to show its support to the Pakistani people, flew hundreds of helicopter missions to drop of food and pick up survivors.
Just as international media interest in the story was peaking, President Asif Ali Zardari was filmed arriving at a family-owned chateaux in France by helicopter, adding fuel to a blaze of criticism at home and abroad over the government's response to the disaster.
This year, media coverage of the disaster has been more muted, but the government has come under some criticism.
Gilani recently returned from a trip to Iran, where he met President Mahmoud Ahmadinejad, while Zardari visited London last week for a health checkup.