The US has criticised Egypt after an appeal court refused to hear a plea by Ayman Nour, an opposition leader jailed for five years.
Ayman Nour was convicted of forging signatures on a petition
Nour was a distant runner-up in last year's presidential election but was later convicted of electoral forgery.
The US criticised the latest decision, calling the verdict a "miscarriage of justice" and a setback for democracy.
Nour's supporters said the court's decision made it likely that he would serve his full five-year sentence.
He maintains that the sentence is politically motivated and intended to remove him from public life.
In Washington, State Department spokesman Sean McCormack criticised the ruling.
"The Egyptian government's handling of this case represents both a miscarriage of justice by international standards and a setback for the democratic aspirations of the Egyptian people," he said.
The court verdict and US criticism came as hundreds of members of another opposition party, the Muslim Brotherhood, were arrested in Cairo following street protests.
Mr McCormack expressed concern over the developments, which "raise serious concerns about the path to political reform in Egypt".
Nour's wife, Gameela Ismail, told the Associated Press news agency the decision not to allow an appeal reflected badly on the government of Egyptian President Hosni Mubarak.
"This verdict proves for the 1,000th time that Mubarak and his regime are controlling the judicial, executive and legislative authorities in Egypt - the bodies whose independence Nour was fighting for."