Two senior senators called on Sunday for Washington to nearly triple military force levels in Iraq to 10,000 and send an equal number of troops to Syria as part of a multinational ground force to counter Islamic State in both countries.

Republicans John McCain and Lindsey Graham criticised Barack Obama’s incremental Islamic State strategy, which relies on airstrikes and modest support to local ground forces in Iraq and Syria, and said the need for greater US involvement was underlined by this month’s Paris attacks.

“The only way you can destroy the caliphate is with a ground component,” said Graham, who is seeking his party’s presidential nomination. “The aerial campaign is not turning the tide of battle.”

McCain, chairman of the Senate armed services committee, recently proposed intervention in Syria by a European and Arab ground force backed by 10,000 US military advisers and trainers.

On Sunday, he and Graham told reporters during a visit to Baghdad that US personnel could provide logistical and intelligence support to a proposed 100,000-strong force from Sunni Arab countries like Egypt, Turkey and Saudi Arabia. Graham said special forces would also be included.

Obama last month ordered the deployment of dozens of special operations troops to northern Syria to advise opposition forces in their fight against Islamic State, adding to an increasingly volatile conflict in Syria.

Russia and Iran have ramped up their military support for President Bashar al-Assad’s fight against rebels in Syria’s four-and-a-half year civil war, while the Paris attacks, in which 130 people died and hundreds were injured, showed how Isis has extended its reach to western cities.

US counter-terrorism experts have warned that deploying ground troops risks backfiring by feeding Isis’s apocalyptic narrative that it is defending Islam against an assault by the west and its authoritarian Arab allies....