The United States, France and Britain pressured Rwanda on Sunday over its support for rebels rapidly closing in on eastern Congo's largest city, as government forces struggled to halt an offensive that has forced thousands of civilians to flee.

Congo has severed diplomatic ties with Rwanda as fighting between Rwanda-backed rebels and government forces rages around the key eastern city of Goma, leaving at least 13 peacekeepers and foreign soldiers dead and displacing thousands of civilians.

Rebels in Democratic Republic of Congo are closing in on a key city in the mineral-rich region aided by neighboring Rwanda’s army, the head of a peacekeeping mission told United Nations Security Council members during an emergency meeting on Sunday.