Manouchehr Mottaki, the Iranian foreign minister, made the announcement on Sunday at the end of a conference in Tehran to raise funds for the Palestinians.
Hamas, meanwhile, said it still hoped to form a unity government, after a meeting with other Palestinian factions including Islamic Jihad and the Popular Front for the Liberation of Palestine.
The US and EU said last week they would suspend aid unless Hamas agreed to renounce violence and recognise the state of Israel.
The EU had been giving about $600 million a year in aid to the Palestinian Authority.
Mottaki said: "We warn that if the aid is cut and if this continues in the near future, this land will witness a humanitarian disaster."
Khalid Mishaal, a Hamas leader who was attending the conference, urged Muslim countries to give aid to the Palestinian Authority.
He said Hamas had inherited an empty treasury and $1.7 billion in debts after their election win in January.
"$170 million dollars a month is needed to run the administration, out of which $115 million goes to paying salaries," said Mishaal.
Amid growing tensions with rival factions, a Hamas spokesman has said the door remains open for Fatah to join it in a unity government.
"We affirmed the issue of forming a national unity government is under consideration," Ghazi Hamad said in Gaza city on Sunday.
Fatah has rejected similar offices and did not attend Sunday's meeting.
Tensions between Hamas and Fatah have risen after Ismail Haniya, the Palestinian prime minister, accused the president, Mahmoud Abbas, of undermining the new government.
The infighting, along with Israeli military action in the northern Gaza Strip, has compounded the problems of the newly formed Hamas government.