Washington, Sep 11 (IANS) US President Barack Obama Wednesday called Saudi King Abdullah about his plan to fight the Islamic State (IS) militants just a few hours before he addressed the American public and the world on the threat posed by the Sunni militant group.

In their phone conversation, the two leaders discussed "their shared concerns" about the threat and agreed on the need for " increased training and equipping" of the moderate Syrian opposition, Xinhua quoted the White House as saying in a statement.

In his prime-time speech Wednesday evening, Obama mapped out a "comprehensive strategy" to "degrade and ultimately destroy" the IS. He announced to send 475 more US military advisers to Iraq, who would not have combat mission, a White House official said.

Obama also did not rule out military intervention in Syria. He said the "US comprehensive and sustained counter-terrorism strategy aims to degrade and destroy IS".

The militant group announced the establishment of a caliphate in late June in areas under its control in both Syria and Iraq, and has beheaded two American journalists.

US warplanes have bombed its targets in northern Iraq since Aug 8, and Obama approved surveillance flights over Syria in late August.

Secretary of State John Kerry arrived in the Middle East region overnight to push for Washington's efforts for building a regional coalition, and is scheduled to meet with his counterparts from ten Arab countries and Turkey in the Saudi city of Jeddah Thursday.