In an interview with PBS television's Charlie Rose ahead of the UN General Assembly meeting in New York, President Mohamed Morsi said the diplomatic quartet of Egypt, Iran, Saudi Arabia and Turkey could help end the 18-month-old conflict in Syria.
"I am against foreign intervention by force in what happens in Syria," Morsi said. "I do not condone this and I think that it is a big mistake if it happens," he added through an interpreter. "Egypt does not agree to this."
Morsi, a former senior member of the Muslim Brotherhood who became Egypt's first democratically elected president in June, said Arab nations should "support the people of Syria in their march toward freedom.
"President Assad has no choice but to leave," Morsi added. "There is no room for political reform. Change is what the people want, and the will of the people must be respected," he added.
"The regime should have realized that the military solution would not stop the revolution. Tens of thousands of people have been killed and more could follow, so the main thing is to stop the bloodshed."
Morsi said he had brought together officials from Egypt, Iran, Saudi Arabia and Turkey in a bid to find a solution to the conflict, in which Syrian activists say more than 29,000 people have been killed.
The Syrian government has accused Saudi Arabia and Turkey of arming opposition rebels, while UN experts have said Iran is arming Assad's forces.
"This is the reason why I chose these countries," Morsi said. "You cannot solve the problem without those countries which intervene in the problem. The stakeholders are the ones who sit down together to solve the problem."
The Egyptian leader added that he hoped he could bring together the heads of states of the four nations to discuss the civil war.
Morsi is to speak at the UN General Assembly on Wednesday.