US President Barack Obama meets with Saudi King Salman at Erga Palace upon his arrival for a summit meeting in Riyadh, Saudi Arabia April 20, 2016. [Photo/Agencies]

RIYADH - US President Barack Obama on Wednesday met with Saudi King Salman bin Abdulaziz here in efforts to mend ties with the old-time ally before leaving office in January next year.

Obama underscored the importance of accelerating the campaign against the Islamic State and welcomed Saudi Arabia's important role in the coalition against the terrorist group, read a White House statement.

The two leaders also discussed regional conflicts in Syria, Yemen and Iraq, and challenges posed by Iran.

It is Obama's fourth and very likely last visit to the oil-rich Gulf nation. He will also attend a summit with leaders of the Gulf Cooperation Council (GCC) countries.

The kingdom is seen as one of Washington's most strategic allies in the Middle East, but bilateral relations were strained by the nuclear deal reached with Iran last year.

Hours before Obama met King Salman, US Defense Secretary Ashton Carter held talks with his Gulf Arab counterparts on military cooperation and the latest developments in the Middle East, including what were described as Iran's destabilizing activities and IS, said GCC Secretary General Abdullatif al-Zayani.

The GCC countries and the United States have agreed to carry out joint patrols to stop any Iranian arms shipments reaching Yemen, al-Zayani told a press conference.

The US defense chief urged the GCC members to be more engaged in helping the Iraqi government fight IS and to rebuild areas where the militants have been pushed out.

The GCC comprises Bahrain, Kuwait, Oman, Qatar, Saudi Arabia, and the United Arab Emirates.