Egyptian opposition leader Mohamed ElBaradei says Egypt must change and he is ready to lead the transition if asked.
Mr ElBaradei spoke at Vienna airport as he prepared to return to Cairo to join street protests there.
Meanwhile, security forces have shot dead an anti-government protester in the Sinai region, witnesses say.
The government says the protests are illegal. Up to 1,000 people have been arrested.
The shooting in Sinai brings the death toll to seven since the protests began on Tuesday.
"If [people] want me to lead the transition, I will not let them down," Mr ElBaradei told journalists at Vienna airport.
