The office of Egypt's president-elect Mohammed Mursi is to take legal action against the Iranian Fars news agency for fabricating an interview with him, the official Mena news agency said.
Fars quoted Mr Mursi saying the two countries should improve ties.
Such a move would go against Western efforts to isolate Tehran over its controversial nuclear programme.
Mena quoted Mr Mursi's spokesman, Yasir Ali, as saying the interview was entirely made up.
Ties between Cairo and Tehran have been frosty since Iran's 1979 Islamic Revolution and the Egyptian-Israeli peace deal of the same year.
The two countries do not have full diplomatic relations but each has a mission in the other's capital.
Fars said that Mr Mursi had "underlined his enthusiasm for the further expansion of ties with Iran, and said relations between Tehran and Cairo will create a strategic balance in the region".
On Monday, Iranian President Mahmoud Ahmadinejad congratulated Mr Mursi for winning the election, state TV reported, adding: "I emphasise expanding bilateral ties and strengthening the friendship between the two nations."
Prior to his election, Mr Mursi was leader of Egypt's main Islamist party, the Freedom and Justice Party.