Nur, a member of parliament, was freed 10 days ago after six weeks in preventive detention. His arrest had provoked global outrage led by the US over "political repression" in Egypt.
The opposition leader who is likely to run against Husni Mubarak in the upcoming presidential elections faces charges of forging signatures for registering his al-Ghad Party.
But the Egyptian attorney-general's announcement that Nur would face trial has evoked muted reaction.
US State Department deputy spokesman Adam Ereli merely said Washington would monitor the proceedings against Nur closely and called on Cairo to handle the case fairly and openly.
"I think we all have an interest in the advancement of transparency, political pluralism and the rule of law in Egypt and throughout the region, including as it applies to the Ayman Nur case," Ereli said.
Nur's arrest was part of the reason that US Secretary of State Condoleezza Rice cancelled a planned trip to Cairo earlier this month.
A senior State Department official, who asked not to be named, said Washington did not want to go too far in commenting on the case until it played out in the courts.
"What we're looking for is a respect for this guy's right to conduct political activity, signs that the government is not harassing an independent party," the official said.
"Certainly we'll be watching closely with particular attention paid to any indication that this is an attempt to circumscribe independent political activity."