Prime Minister Yousuf Raza Gilani of Pakistan has cancelled a trip to next week's UN General Assembly in New York because of floods in Sindh province.
His office said he was staying in the country to direct relief efforts.
Pakistani leaders were accused of neglecting victims of floods that swept the country last year and are accused of being slow to respond once again.
About six million people have been affected so far this year. The BBC reports there are fears some areas will remain submerged for months.
At least 269 people are confirmed to have died.
The government is accused of being months behind schedule in repairing dams and embankments damaged by last year's floods.
Mr Gilani has been in Iran in recent days, while President Asif Ali Zardari flew to London last week on a private visit.
The prime minister's office now says he ''will visit flood-affected areas from tomorrow and supervise relief efforts''.
Foreign Minister Hina Rabbani Khar will address the General Assembly in his place.
Mr Zardari was heavily criticised for visiting Britain in August 2010 when Pakistan was hit by its worst floods in living memory.
People in Sindh have told the BBC they are angry that the authorities have not done more in the wake of that disaster.
They say flood prevention projects and proper drainage systems could have saved homes and lives and an awful lot of misery.