The US Secretary of State John Kerry used a surprise visit to Egypt to call for fair and transparent trials for all Egyptians.
The unscheduled trip is Mr Kerry's first since the former President was ousted.
It comes just a day before the former President is due to appear in court.
Mr Mursi has been charged with inciting violence prior to his overthrow
US Secretary of State John Kerry has described Egypt as a 'vital partner' in the region and said he could see indications that Egypt was moving towards democracy.
He said that the road-map is being carried out to the best of our perception.
Mr Kerry acknowledged that last month's decision by President Barack Obama to freeze some military aid as well as $260m (€192m) in cash and this is pending progress on democracy and human rights, had not gone down well in Cairo.
He said that President Obama has actually worked very, very hard to be able to make certain that we're not disrupting the relationship with Egypt.
Egypt has long been the second largest recipient of US aid after Israel, with the military receiving $1.3bn a year.
However, Egyptian Foreign Minster Nabil Fahmy told Reuters yesterday that Egypt would look beyond the United States to meet its security needs.
Washington has also held up the delivery of four F-16 fighter jets to the Egyptian air force.
Ties between the US and Egypt have deteriorated since the overthrow of Islamist President Mohammed Mursi.
Washington has repeatedly urged the interim government to act with restraint in cracking down on the Muslim Brotherhood and its supporters.
But today, Mr Kerry stressed that the United States and the American people support the Egyptian people.
Mr Kerry's visit took place a day before Mursi and 14 other senior Muslim brotherhood leaders were due to go on trial charged with inciting violence.