WASHINGTON (AP) — The leaders of the United States and five other Western powers are calling for an immediate cease-fire in the Syrian city of Aleppo.

President Barack Obama is joining with the leaders of Britain, Germany, Italy, France and Canada in a joint statement demanding that Syria's government address the humanitarian crisis by allowing U.N. aid in to eastern Aleppo.

They're accusing Russia of obstruction at the Security Council. The leaders say Russia and Iran claim to want to work toward a political solution but are unwilling.

The leaders want the United Nations to investigate reports that war crimes are being committed in Syria.

The statement comes as several Syrian rebel factions are proposing a five-day cease-fire in the eastern part of Aleppo to allow civilians to be evacuated.