A US official said the Egyptian government was going "way too far" in the crackdown on the Brotherhood, but added that the Obama administration was not planning to take any action against Cairo in response.
The US official said that the administration of President Barack Obama was not considering, or even discussing, the possibility of the US government designating the Muslim Brotherhood as a terrorist organization.
Historically, the US has placed the names of some individuals associated with the Muslim Brotherhood on US government sanctions list, but has not imposed sanctions on the movement itself.
In Washington, US Secretary of State John Kerry called Egyptian Foreign Minister Nabil Fahmy and "expressed concern" about the terrorist designation of the Muslim Brotherhood and recent detentions and arrests in Egypt, State Department spokeswoman Jen Psaki said.
Kerry condemned the recent bomb attacks in Egypt but "underscored the need for an inclusive political process across the political spectrum that respects the fundamental human rights of all Egyptians in order to achieve political stability and democratic change," Psaki said.