DAR ES SALAAM, July 2 (Reuters) - U.S. President Barack Obama called embattled Egyptian President Mohamed Mursi to urge him to respond to mass opposition demonstrations and said the political crisis could only be resolved by talks, the White House said on Tuesday.

Obama also called on both sides to ensure rallies stayed peaceful, after the death toll in clashes between rival protesters since Sunday reached at least 16 people.

Egypt's armed forces on Monday handed the president a virtual ultimatum to share power, giving feuding politicians 48 hours to compromise or have the army impose its own road map.

The president of the United States, which is a big aid donor to Egypt and its military, "told President Mursi that the United States is committed to the democratic process in Egypt and does not support any single party or group," the White House said.

"President Obama encouraged President Mursi to take steps to show that he is responsive to their concerns, and underscored that the current crisis can only be resolved through a political process," it said in a statement.

Obama, who is in Tanzania at the end of an eight-day visit to Africa, urged Mursi to create an inclusive political process.

"Democracy is about more than elections," the statement said. "It is also about ensuring that the voices of all Egyptians are heard and represented by their government, including the many Egyptians demonstrating throughout the country."

Obama repeated his concern about reports of violence during rallies, particularly reports of sexual assaults against women. He urged Mursi to make clear to his supporters that all forms of violence were unacceptable, the statement said.

(Reporting by Mark Felsenthal; Editing by Edmund Blair and Duncan Miriri)