IS cannot be defeated without Assad's removal: Saudi FM

Saudi Foreign Minister Adel al-Jubeir has insisted that defeating the Islamic State group in Syria was conditional on the removal of Syrian President Bashar al-Assad from power.

"Unless and until there is a change in Syria, [IS] will not be defeated in Syria," he added.

Jubeir's statement came as he addressed the Munich Security Conference on Friday after joining foreign ministers from global and regional powers in agreeing to seek a temporary "cessation of hostilities" in Syria.

The Saudi foreign minister said his country was working for political change in order to remove "a man who is the single most effective magnet for extremists and terrorists in the region".

"That's our objective and we will achieve it," he added.

In a rare interview published on Friday, Assad revealed his intention to retake "the whole of Syria" by military force.

Earlier this week, the US welcomed a Saudi offer to deploy special forces to support a coalition ground operation against IS in Syria.

Following a meeting with US Secretary of State John Kerry, Jubeir said that any operation would be US-led, but that Saudi Arabia would play a leading role.

"The US government was very supportive and very positive about the kingdom's readiness to provide special forces to the operation in Syria, should the international coalition make a decision to do so," Jubeir told reporters.

"So the kingdom will be part of it," he said. "That support came from the White House, it came from the State Department, it was natural for Secretary Kerry to support such a decision."

On Friday, Kerry said diplomats meeting in Munich had agreed to work with Syrian parties to implement a "nationwide cessation of hostilities".

Kerry said that the target was to implement the ceasefire in a week's time, adding that this would not apply to IS and the Nusra Front, al-Qaeda's franchise in Syria.