WASHINGTON (AFP) - US President Barack Obama spoke by phone with Saudi King Abdullah on Wednesday and met his top national security and intelligence advisors ahead of his prime time speech on the Islamic State in Iraq and Syria ISIS.

Obama called Abdullah from the Oval Office, underlining Saudi Arabia's role as a potentially key member of the international coalition that Obama is trying to build to take on the jihadist group.

The call preceded his speech to the nation at 9 pm Wednesday (9am Thursday Singapore time) about his new strategy to take on ISIS and came ahead of a planned visit to Saudi Arabia by Secretary of State John Kerry.

Obama also gathered what is effectively his war cabinet in the secure Situation Room of the White House. The meeting included Vice President Joe Biden, Secretary of Defence Chuck Hagel, senior leaders of the military and the chiefs of US intelligence agencies.