Egypt's Islamist president met with the nation's top judges on Monday and told them he had acted within his rights when he issued a series of decrees giving him sweeping powers, according to his spokesman.
That stand is likely to trigger a prolonged showdown with the opposition.
Presidential spokesman Yasser Ali told reporters that Mohammed Morsi assured the judges that the decrees did not in any way "infringe" on the judiciary.
Ali's comments signalled Morsi's resolve not to back down or compromise on the steps he announced on Thursday, putting himself and a body writing a new constitution above the judiciary.
Morsi's opponents and supporters plan rival rallies on Tuesday in Cairo.
The judiciary council is in charge of the courts and was the main target of Morsi's edict, which puts him beyond the reach of judicial review until a new constitution and parliament is in place.
In a statement released Sunday night, the Supreme Judicial Council said Morsi's decree should apply only to "sovereign matters."
The opposition has denounced the decrees as dictatorial, and vows to press on with street protests until Morsi rescinds them.
Morsi has said the new powers are needed to push through democratic reforms, after decades of rule by ousted president Hosni Mubarak.