Vote on Friday will be last chance to elect president and avert political crisis.
He said that Saad al-Hariri, the parliamentary majority leader, would then name a prime minister from outside his Future bloc to form a national “reconciliation government”.
The deal would also give the opposition 45 per cent of the seats in a new national unity cabinet.
Aoun has previously refused to consider any other person for the presidency, pointing out that he is the only figure to have received more than 70 per cent of the Christian vote in past elections.
She also said that Hezbollah, which is Aoun’s partner in the opposition, was expected to support his plan.
“They are allies, they signed a co-operation agreement earlier this year, they are stauch supporters,” she said.
“It is highly unlikely Aoun would come up with this initiative without discussing it with his allies.”
Aoun’s announcement came after a member of the ruling bloc told the AFP news agency that a parliamentary session would not take place.
“Friday’s session has been postponed,” Solange Gemayel said. She said the postponement of the session would be officially announced by Nabih Berri, parliament’s speaker.
Four previous parliamentary sessions at which a new president should have been named have been postponed over the past two months.
According to the Lebanese constitution, if no candidate is chosen by parliament to replace Lahoud, the outgoing head of state hands over power to the government, which can then pursue talks on a compromise candidate.
Lahoud has said he will take action before leaving office if no deal is reached on a successor, but he has not said what he plans to do.
“I stand by my position that this government is illegitimate and unconstitutional. If it thinks it can go on without the election because of outside backing, it will bring catastrophes on the country sooner or later,” Lahoud’s office quoted him as telling a Hezbollah-led delegation.
“Therefore, even if I stand alone, there are duties I must perform. My conscience is clear and I hope it will be good for Lebanon.”