CAIRO (Reuters) - President Barack Obama has invited Egypt's newly elected Islamist president, Mohamed Mursi, to visit the United States in September, an Egyptian official said on Sunday, reflecting the new ties Washington is cultivating with the region's Islamists.

"President Obama extended an invitation to President Mursi to visit the United States when he attends the U.N. General Assembly in September," Egyptian aide, Yasser Ali, said after Mursi met U.S. Deputy Secretary of State William Burns.

Burns did not mention the invitation at a news conference earlier.

Washington, long wary of Islamists and an ally of ousted President Hosni Mubarak, shifted policy last year to open formal contacts with the Muslim Brotherhood, the group behind Mursi's win. Mursi formally resigned from the group when he won the presidency.

(Reporting by Marwa Awad; Writing by Edmund Blair; Editing by Andrew Osborn)