CAIRO, Nov 24 (Reuters) - Prominent opposition leader Mohamed ElBaradei said on Saturday there could be no dialogue with Egypt's president until he rescinded a "dictatorial" decree that he said gave the Islamist leader Mohamed Mursi the powers of a pharaoh.

The presidential decree issued on Thursday by Mursi, elected in June with the Muslim Brotherhood behind him, expanded his powers and caused fury amongst his opponents, prompting violent clashes in central Cairo and other cities on Friday.

Judges, angry at measures seen as undermining the judiciary, have threatened to strike if the declaration was not revoked and the opposition has called for more protests, with one planned for Tuesday.

"There is no room for dialogue when a dictator imposes the most oppressive, abhorrent measures and then says 'let us split the difference'," ElBaradei said in an interview with Reuters and The Associated Press after talks with opposition figures.

ElBaradei, who said he expected to be coordinator of a new opposition National Salvation Front, said Mursi's declaration threatened Egypt's troubled transition to democracy and actions were needed to stop a "cycle of violence".

"How are we going to do that? I do not see any other way other than through Mr. Mursi rescinding his dictatorial declaration," he said, adding the decree created a "new pharaoh".

In his decree, Mursi put all his decisions beyond legal challenge as long as there is no parliament, sacked the unpopular general prosecutor and opened the door to retrials for the already jailed ousted president Hosni Mubarak and his aides.

"I am waiting to see, I hope soon, a very strong statement of condemnation by the U.S., by Europe and by everybody who really cares about human dignity," ElBaradei said, speaking from his villa on the outskirts of Cairo.