The White House says it is concerned by a "campaign" of arrests of Egyptian opposition activists in the run-up to local elections next month.
The Brotherhood says only a few candidates are allowed to stand
The vote's integrity was being called into question, a spokeswoman said.
Hundreds of members of Egypt's main opposition Muslim Brotherhood group have been arrested since February.
The Muslim Brotherhood is officially banned in Egypt but members standing as independents currently hold a fifth of the seats in parliament.
The Brotherhood says the authorities are holding more than 730 members in custody, and have detained more than 350 in the last month.
Observers say the detentions have coincided with the 10-day registration period for candidates in the key council elections on 8 April.
"We are concerned by a continuing campaign of arrests in Egypt of individuals who are opponents of the current governing party and are involved in the upcoming local elections," White House spokeswoman Dana Perino said.
"The people of Egypt should be permitted to choose freely among competing candidates.
"We call on the government of Egypt to cease any actions that would compromise the ability of the Egyptian people to fully exercise their internationally recognised human rights and to participate in a free and fair election."
Correspondents say Egypt's 4,500 local councils are key institutions in the country's centralised system of state control.
The Brotherhood says government interference means only 60 of its thousands of candidates have been allowed to register.