This week, French President Francois Hollande also asked for an explanation from Obama following allegations of US spying on millions of French phones.
The latest spying allegations come months after European media reported, based on the information leaked by Edward Snowden, that the US national security agency had bugged EU offices.
European Council President Herman Van Rompuy insisted Thursday that the summit would still discuss economic and social issues, adding that growth could return to most EU member states in the coming year.
But the summit's planned topics could be further overshadowed by immigration concerns in the aftermath of a shipwreck off an Italian island. British Prime Minister David Cameron has urged EU institutions to cut red tape on business.
