WASHINGTON (Reuters) - Qatar is committed to defeating the Islamic State in Iraq and Syria (ISIS), its emir assured United States President Barack Obama on Tuesday in his first official visit to the White House.

Mr Obama said Sheikh Tamim Bin Hamad al-Thani committed to fighting Islamic extremists and supporting the moderate opposition in Syria. Qatar is part of the US-led coalition fighting ISIS, which controls a wide swathe of territory in Syria and Iraq.

The two leaders are "deeply concerned" about the situation in Syria and shared ideas on how they can transition Syrian President Bashar al-Assad out of power, Mr Obama told reporters in the Oval Office. "We'll continue to support the moderate opposition there, and continue to believe that it will not be possible to fully stabilise that country until Mr Assad, who has lost legitimacy in the country, is transitioned out," Mr Obama said. "How we get there obviously is a source of extraordinary challenge, and we shared ideas in terms of how that can be accomplished."

In the past, there has been suspicion that money has gone from Qatar to violent extremist groups in the region. Mr Obama "stressed the need for continued cooperation between our officials in countering terrorist financing", a senior US administration official said.

The two leaders also discussed the ongoing unrest in Libya and Yemen, the official said.

The emir said Mr Obama told him he was committed to a peace process between Israel and Palestinians.

"I'm happy to learn and to hear from you, President, that you are committed to find this peace process in Palestine," he said to Mr Obama in front of reporters in the Oval Office.