MANAMA (Reuters) - The United States will send 200 additional military personnel including special forces to the campaign against Islamic State in Syria to create a “tornado” of pressure against the group’s Raqqa hub, U.S. Defense Secretary Ash Carter said on Saturday,

U.S. Defense Secretary Ash Carter attends a meeting with Japan's Defense Minister Tomomi Inada at the Defense Ministry in Tokyo, Japan, December 7, 2016. REUTERS/Kazuhiro Nogi/Pool

Carter, speaking in Bahrain to regional security chiefs, twinned the announcement with a call on Middle East allies to do more for their own defense, a sore topic with some Gulf states who resent being seen by Washington as military “free riders”.

The arrival of the 200 additional forces in Syria, joining 300 special forces already there backing local allies, would bring to bear the “full weight of U.S. forces around the theater of operations like the funnel of a giant tornado”, Carter said.

“The sooner we crush both the fact and the idea of an Islamic state based on ISIL’s barbaric ideology, the safer we’ll all be”, he said at the Manama Dialogue security conference.

Syria’s civil war pits Assad, backed by Iran, Russia and some Shi’ite militias, against mostly Sunni Arab rebels backed by Turkey, Gulf monarchies and the United States. A secondary conflict puts all of them at war with Islamic State.

Mosul in Iraq and Raqqa in Syria are the pillars of Islamic State’s self-declared caliphate, and recapturing them would be a pivotal defeat for the ultra-hardline Sunni jihadists.

Carter said that despite the eventual defeat of IS in Syria the violence there would not stop until an end was put to the civil war, and Russia’s intervention to back President Bashar al-Assad had only inflamed the conflict.

Russia entered into the war saying it wanted to promote a smooth political transition and fight IS, Carter said.

“But then it did neither of those things,” he added.

ALLIES “AREN’T DOING ENOUGH”

Syrian army advances in Aleppo mean the government appears closer to victory than at any point since 2011 protests against Assad evolved into an armed rebellion. The war has killed more than 300,000 people and made more than half of Syrians homeless.

In Iraq, Carter said, his main concern that the effort to stabilizes the Mosul region after it was liberated, by rebuilding towns, services and communities, “will lag behind the military campaign”. Gulf countries could help with that.

Carter reiterated a U.S. call for more defense cooperation among Gulf Arab states, a delicate question ever since President Barack Obama last year told The Atlantic magazine some states in the Gulf and Europe were “free-riders” who called for U.S. action without getting involved themselves.

Some Gulf states see Obama, keen to extricate Washington from conflicts across the world, as unappreciative of their willingness to host U.S. bases and purchase U.S. weapons.

“Mutual interest requires mutual commitment,” Carter said. “I would ask you to imagine what U.S. military and defense leaders think when they have to listen to complaints sometimes that we should do more, when it’s plain to see that all too often, the ones complaining aren’t doing enough themselves.”