WASHINGTON -- U.S. President Barack Obama has spoken with Prime Minister Stephen Harper about chemical weapons use in Syria.

The two leaders talked by phone Monday as Obama was seeking congressional approval for a military strike in Syria but also was considering a potential deal for Syria to turn over its chemical weapons stockpiles to avoid a U.S. attack.

The White House says Obama and Harper agreed there must be a strong international response to chemical weapons use to ensure that similar atrocities won't occur in the future.

Canada is among two dozen countries that have signed a joint statement blaming the government of Syrian President Bashar Assad for using chemical weapons in an attack last month outside Damascus. The statement doesn't explicitly call for military action.