He added that recovering from the floods would take at least three years.
The IMF has said the floods will present "a massive economic challenge" to Pakistan and that it will look at ways it can assist.
"The IMF stands with Pakistan at this difficult time and will do its part to help the country," the organisation said in a statement on Saturday.
Because of the floods, Pakistan fears it might not be able to meet inflation and deficit targets set by the IMF as part of the fund's loan package.
Various estimates put the country's economic growth this year at anywhere from zero to 3 per cent, less than the government's target of 4.5 per cent, according to the Reuters news agency.
The fiscal deficit is also predicted to expand to more than 8 per cent of gross domestic product.
Pakistan's agricultural sector has been particularly hard hit.
The floods have destroyed or severely damaged more than 1.7 million hectares of crops, around 18 per cent of the country's cultivable land, Nazar Muhammad Gondal, Pakistan's minister of food and agriculture, told Reuters on Monday.
International donors have pledged more than $800 millionto help Pakistan deal with the floods, which have killed around 1,500 people and made six million homeless over the past three and a half weeks.
The government is under pressure to respond but will have to engage in creative financing amidst Pakistan's troubled economy.
Shah Mehmood Qureshi, the foreign minister, said in New York City on Thursday that the government would "revisit" its budget and expected to cut spending while diverting to flood recovery some of the $7.74 billion allocated to development projects.
"Either the [IMF] steps forward and allows plenty of relaxations on the current programme or we make a fresh start and discuss a new programme with performance criteria that are tailored to our new economic realities," a Pakistani official told the Financial Times newspaper last week.
"The present program is not looking sustainable."