Clashes erupted Monday on the streets of Cairo not long after a visiting U.S. diplomat hailed what he called a "second chance" for democracy after the ouster of Egypt's elected president this month.

Deputy Secretary of State William Burns, the highest-level U.S. official to visit Cairo since President Mohammed Morsi was removed by the military on July 3, signaled Washington's readiness to stand with Egypt's new leaders even as Morsi supporters were gathering for fresh demonstrations to demand his reinstatement.

"The United States is firmly committed to helping Egypt succeed in this second chance to realize the promise of the revolution," Burns said after meeting with members of the new interim government.

Burns' language seemed to underline a shift by the White House in the past two weeks, from warning against unseating a democratically elected president to throwing its weight behind the backers of the coup.

Underscoring the challenge ahead for the U.S., Burns was rebuffed by representatives of both the group that led the popular uprising against Morsi and the ultraconservative Islamist party that could benefit from the ouster.