Barack Obama arrives in Saudi Arabia

US President Barack Obama arrived in Saudi Arabia for talks with King Salman and other leaders from Gulf Cooperation Council (GCC) countries.

Relations between the US and its Saudi ally have become strained over the fight against so-called Islamic State (IS) and the nuclear deal with Iran.

Secretary of State John Kerry and Defence Secretary Ashton Carter are on the trip with the president.

After talks with King Salman on Wednesday, Obama will meet the leaders of Kuwait, Qatar, Bahrain, the United Arab Emirates and Oman on Thursday. He will then travel to the UK and Germany.

The US-Saudi relationship has been badly strained by a deal between Western nations and Iran to curb its nuclear programme, a move that Riyadh and its allies feared would embolden Tehran in the region.

"We stressed that if Iran wants to have normal relations with GCC states it has to change its policies and to abide by the good neighborhood principle and to refrain from interfering in the affairs of GCC states and the countries of the region," the Saudi Foreign Minister Adel Al-Jubeir said earlier this month.

Syria will also be high on the agenda, with both the US and Saudi Arabia wanting President Bashar al-Assad to go, and both backing opposition groups fighting him. The Islamic State of Iraq and the Levant (ISIL) - and the efforts of a US-led coalition backed by Riyadh to fight it - will also be discussed.

Separately, Riyadh leads a coalition that more than a year ago began a campaign of air strikes to support Yemen's government in a battle against Iran-backed Houthi rebels.

Another bone of contention overshadowing the visit is proposed US legislation that could pave the way for the Saudi state to be sued in US courts over the September 11 attacks. 

Fifteen of 19 hijackers on that day were Saudi citizens. Saudi government complicity in the attacks, though, has never been proved.

Riyadh has threatened to sell $750bn worth of US assets if the proposed bill passes.