Egyptian opposition leader Ayman Nour has been formally charged with forging signatures to register his party.
Nour has announced he will stand against President Mubarak in elections
Mr Nour will stand trial in a criminal court along with six other defendants from his party, al-Ghad, or Tomorrow.
Mr Nour, a prominent advocate of political reform in Egypt, says he will stand against President Hosni Mubarak in elections due in September.
Washington has expressed very strong concerns over the case and expressed hope that it will be resolved soon.
Mr Nour was freed on bail earlier in March, nearly six weeks after being arrested for allegedly forging election papers.
Supporters Mr Nour insist charges against him were trumped up.
Egyptian officials have insisted the case is a legal, not political, matter.
Credible opposition candidate
Police had seized Mr Nour, an MP, as he left parliament on 29 January and he was accused of forging all but 14 of more than 2,000 signatures required to form his party.
Some analysts believe Mr Nour, a former journalist, lawyer and publisher, possesses the necessary profile to make substantial inroads against the president.
Mr Mubarak agreed to allow challengers to contest the election after demonstrations by pro-democracy campaigners defying a ban on street protests and amid pressure from the US.