State Department spokesman P.J. Crowley says Clinton condemned the violence and told Suleiman the government should hold to account those responsible.
Crowley says the U.S. does not know who unleashed what he called "thugs." He called the clashes a clear attempt to intimidate protesters.
Protesters claimed plainclothes police were among several thousand supporters of President Hosni Mubarak (HAHS'-nee moo-BAH'-rahk) who attacked anti-government demonstrators in Cairo on Wednesday.
Suleiman is an intelligence chief. He was appointed vice president last week in Mubarak's first major response to the unrest.