The White House on Wednesday condemned the violence sweeping across Egypt, warning the country's military-backed interim government that "the world is watching."
At least 149 people were killed in Egypt on Wednesday, many in assaults on protest vigils among supporters of ousted President Mohammed Morsi.
Egypt's interim President declared a monthlong state of emergency, ordering the armed forces to support police in efforts to restore law and order.
President Barack Obama, in the middle of a weeklong vacation in Massachusetts, was briefed on the deteriorating situation Wednesday, spokesman Josh Earnest said.
"The violence will only make it more difficult to move Egypt forward on a path to lasting stability and democracy and runs directly counter to the pledges by the interim government to pursue reconciliation," Earnest said.
The White House comments largely echoed its previous statements since the democratically elected Morsi was ousted on July 3.
The US has said it does not plan to label Morsi's ouster a coup, and officials on Wednesday indicated no change in that position following the latest violence. By law, the US would have to cut off $1.3 billion in aid to Egypt if it determined that the ouster had been a coup. Officials say taking such a step would not be in the US interests.
Wednesday's assault came after days of warnings by the interim administration. The two sit-in camps at two major intersections on opposite sides of the Egyptian capital began in June to show support for Morsi.
The protesters - many from Morsi's Muslim Brotherhood - have demanded his reinstatement.
At least 250 people have died in previous clashes.
Earnest said the US would continue to encourage the interim government to make good on its promise to enact political reforms, including amending the Islamist-backed constitution adopted last year and holding parliamentary and presidential elections early next year.
"Figuring out how to encourage the interim government to make good on their promise to transition to a democratically elected government there is something that we're working on." Earnest said. "Hopefully, it's something they're working on."