El-Baradei, former head of the International Atomic Energy Agency (IAEA), returned to Egypt on the eve of the protests which swept the country on Friday, when tens of thousands of people called for the overthrow of President Hosni Mubarak.

El-Baradei and the powerful Muslim Brotherhood said on Sunday he had a mandate from opposition groups to make contact with the army and negotiate a government of national unity. At least one opposition party, the Arab nationalist Karama Party of Hamdin Sabahi, has rejected El-Baradei outright as a transitional figure, saying he was trying to jump on the bandwagon of the popular uprising.

El-Baradei joined protesters at the hub of anti-Mubarak protests in central Cairo on Sunday. The official media tried to ridicule him, saying he knew nothing about Egypt and had no political experience.

Some elements of the government’s campaign appear to have stuck. “El-Baradei won’t do. He doesn’t have the experience here and he’s a little weak,” said Khaled Ezzat, 34, an information technology engineer who had joined the evening vigil in Tahrir Square. Omar Mahdi, a sales manager, said: “I’m not convinced by El-Baradei, even as a transitional figure, he hasn’t really been present in the country.”

Some of the protesters objected to El-Baradei on the grounds that he was too close to the US, despite the frictions between him and the US administration over the Iranian and Israeli nuclear programs when he was head of the IAEA.

“El-Baradei’s positions toward other Arab countries, and toward Iran and North Korea, were not neutral... So I don’t find him very acceptable,” said Walid Abdel-Mit’aal, 36, who works for a public sector company. “He would follow Mubarak in the same policies and would take US aid,” he added, reflecting an anti-American strand which was largely absent in the first four days of protests.

El-Baradei’s cosmopolitanism — he lived abroad for years and speaks fluent English — may be an advantage among some Egyptians but it is also a source of suspicion among others.

The protesters in Tahrir Square suggested several alternatives to El-Baradei as transitional leader, including Arab League Secretary General Amr Moussa, a popular former foreign minister, the president of the constitutional court or the president of the supreme administrative court.

Others said they were open-minded and what mattered was changing the constitution to ensure that no one man clings to power as long as Mubarak, who took office in 1981.

“El-Baradei is a very acceptable option because he will not stay,” said Islam Ashraf, 24, a quality operations coordinator. “But we’re not really interested in faces. What matters to us is having another system,” he said.