The United Nations and Islamabad will launch a formal appeal Tuesday for $160 million to fund emergency aid for Pakistan, which is battling the worst monsoon floods in a decade.

Pakistani officials say over 1,100 people have died since June, when the seasonal rains started, but the final toll could be higher. This year's flooding has affected more than 33 million people -- one in seven Pakistanis.

"The situation is expected to worsen with more ongoing rainfall," Stephane Dujarric, the UN Secretary-General spokesman, said during a press briefing Monday.

"We along with the (Pakistani) government are planning a flash appeal of $160 million for immediate relief activities," he said, noting the request will officially launch Tuesday.

The UN has "already mobilized about $7 million, including redirecting existing programs and resources to meet the more urgent needs" such as food, water, medical supplies and shelter.

An additional $3 million has been released by the United Nations emergency response fund.