US Secretary of State John Kerry has called for a global coalition to combat Islamic State extremists and their “genocidal agenda”.
His comments came as Saudi Arabia’s King Abdullah warned the West would be the jihadist group’s next target unless there was urgent action to halt its advances through Iraq and Syria.
The UK Government has raised Britain’s terror threat level from substantial to severe because of the threat from militant groups in the Middle East.
Writing in the New York Times ahead of this week’s NATO summit in Wales, Mr Kerry pressed for “a united response led by the United States and the broadest possible coalition of nations”.
He said he and Defence Secretary Chuck Hagel would meet European counterparts on the sidelines of the summit to enlist assistance, and then travel to the Middle East to build support “among the countries that are most directly threatened”.
US President Barack Obama has acknowledged Washington has no strategy yet to tackle the Islamic State, which has declared an Islamic “caliphate” in large swathes of territory under its control in Iraq and Syria.
But Mr Kerry said the US would be putting forward an action plan at a summit meeting of the UN Security Council in September, when Washington will hold the group’s presidency.
“What’s needed to confront its nihilistic vision and genocidal agenda is a global coalition using political, humanitarian, economic, law enforcement and intelligence tools to support military force,” Mr Kerry said.
The Islamic State (IS) has sparked growing alarm in the West at its rapid and brutal advance in both Syria and Iraq, killing hundreds of people, including in gruesome beheadings and mass executions.
The US began carrying out airstrikes against the group in Iraq earlier this month, but has yet to decide if it will expand that military action into Syria.
The cost of American military operations have cost about $560m (337m) since mid-June, according to the Pentagon – an average of 7.5m (4.5m) a day.
Syrian President Bashar al Assad has said he is willing to co-operate in tackling jihadists, but that any military action on its territory must be co-ordinated.
This causes a dilemma for Washington, which has long backed the rebels seeking President Assad’s overthrow, and accuses his regime of rights violations including the use of chemical weapons.