Obama says the U.S. supports non violence and protecting human rights, but was careful not to take sides. The president is calling on the Egyptian military to quickly hold elections and restore a democratically elected Egyptian government.
After the ultimatum deadline expired Wednesday at 5 p.m. local time, Gen. Abdel-Fattah el-Sissi, the country's top military commander, went on state TV and said Mansour would step in as interim president until new elections were held.
The office of the presidency tweeted defiance in his name.
"Measures announced by Armed Forces leadership represent a full coup categorically rejected by all the free men of our nation," read one of a series of tweets in Morsi's name.
"Morsi urges civilians and military members to uphold the law and the constitution not to accept that coup which turns Egypt backwards," the tweets stated.
"President Morsi urges everyone to adhere to peacefulness and avoid shedding blood of fellow countrymen," he concluded.
El-Sissi warned the Egyptian people to protest peacefully and said the authorities would not tolerate any violence.
ABC News' Alex Marquardt, Dana Hughes, Molly Hunter, Luis Martinez and The Associated Press contributed to this report.