Barack Obama Riyadh

President Donald Trump delivered a forceful address here Sunday summoning the Muslim world to confront "the crisis of Islamic extremism" as he seeks to present a united front against global terrorism.

US Defense Secretary Jim Mattis is in Saudi Arabia Wednesday to reinvigorate the Riyadh-Washington alliance, with both seeing a common adversary in Iran and its "destabilising" activities.

US President Barack Obama and Gulf Arab leaders started talks in Riyadh today at a summit aimed at forging joint action on perceived security threats from Iran and Islamic State, and at ironing out strains in their old alliance.

US President Barack Obama arrived in Riyadh on Wednesday to meet Saudi Arabia's King Salman ahead of a summit with other Gulf Arab leaders on Thursday and with regional tensions with Iran likely to be high on the agenda.

US President Barack Obama will make another trip to Riyadh to consult Washington's Gulf allies on the crises in Yemen and Syria this week, but may not receive a royal welcome.

U.S. Defense Secretary Ash Carter said after talks in Saudi Arabia that Iran's "potential for aggression" was a shared concern as he moved to bolster defence ties with Riyadh following a nuclear agreement with its arch-foe.

The White House said Friday that a top Saudi envoy "welcomed" the recent nuclear deal with Iran in a meeting with President Barack Obama, after months of skepticism.

Discontent with American policy toward Iran is behind the last-minute pullout by Saudi King Salman from a summit with US President Barack Obama this week, analysts say.

US President Barack Obama ended a four-nation foreign trip on Saturday in the same situation as he began it - facing great uncertainty about a diplomatic way out of the Ukraine crisis.

Upset at President Barack Obama's policies on Iran and Syria, members of Saudi Arabia's ruling family are threatening a rift with the United States that could take the alliance between Washington and the kingdom to its lowest point in years.

Saudi Arabia, in an unprecedented show of anger at the failure of the international community to end the war in Syria and act on other Middle East issues, said on Friday it would not take up its seat on the United Nations Security Council.

If President Barack Obama has disappointed Syrian rebels by deferring to Congress before bombing Damascus, he has also dismayed the United States' two main allies in the Middle East.

President Donald Trump delivered a forceful address here Sunday summoning the Muslim world to confront "the crisis of Islamic extremism" as he seeks to present a united front against global terrorism.

US Defense Secretary Jim Mattis is in Saudi Arabia Wednesday to reinvigorate the Riyadh-Washington alliance, with both seeing a common adversary in Iran and its "destabilising" activities.

US President Barack Obama and Gulf Arab leaders started talks in Riyadh today at a summit aimed at forging joint action on perceived security threats from Iran and Islamic State, and at ironing out strains in their old alliance.

US President Barack Obama arrived in Riyadh on Wednesday to meet Saudi Arabia's King Salman ahead of a summit with other Gulf Arab leaders on Thursday and with regional tensions with Iran likely to be high on the agenda.

US President Barack Obama will make another trip to Riyadh to consult Washington's Gulf allies on the crises in Yemen and Syria this week, but may not receive a royal welcome.

U.S. Defense Secretary Ash Carter said after talks in Saudi Arabia that Iran's "potential for aggression" was a shared concern as he moved to bolster defence ties with Riyadh following a nuclear agreement with its arch-foe.

The White House said Friday that a top Saudi envoy "welcomed" the recent nuclear deal with Iran in a meeting with President Barack Obama, after months of skepticism.

Discontent with American policy toward Iran is behind the last-minute pullout by Saudi King Salman from a summit with US President Barack Obama this week, analysts say.

US President Barack Obama ended a four-nation foreign trip on Saturday in the same situation as he began it - facing great uncertainty about a diplomatic way out of the Ukraine crisis.

Upset at President Barack Obama's policies on Iran and Syria, members of Saudi Arabia's ruling family are threatening a rift with the United States that could take the alliance between Washington and the kingdom to its lowest point in years.

Saudi Arabia, in an unprecedented show of anger at the failure of the international community to end the war in Syria and act on other Middle East issues, said on Friday it would not take up its seat on the United Nations Security Council.

If President Barack Obama has disappointed Syrian rebels by deferring to Congress before bombing Damascus, he has also dismayed the United States' two main allies in the Middle East.