The US will not intervene in the Syria conflict because it does not believe anti-Assad rebels would support American interests, its highest ranking military officer wrote in a letter to a congressman.

General Martin Dempsey, chairman of the Joint Chiefs of Staff and Barack Obama’s chief military adviser, said that the US military was capable of taking out the Syrian government’s airforce and tipping the deepening struggle back in the favour of the country’s opposition.

But, in an extraordinarily frank assessment, Gen. Dempsey said that approach was not favoured by Washington as it would leave the US mired in another Middle Eastern war and offer little chance of peace in a country wracked by ethnic divisions.

In an August 19 letter to Representative Eliot Engel, obtained by the Associated Press, Gen. Dempsey effectively ruled out even limited intervention, including US cruise missile attacks and other options that wouldn’t require US troops on the ground.

“Syria today is not about choosing between two sides but rather about choosing one among many sides,” he said. “It is my belief that the side we choose must be ready to promote their interests and ours when the balance shifts in their favour. Today, they are not.”

The military chief’s analysis will hardly please members of the fractured Syrian opposition leadership and some members of the Obama administration who have wanted greater support to help the rebellion end Bashar Assad’s four-decade family dynasty.

Despite internal disputes, some opposition groups have worked with the United States and European and Arab supporters to try to form a cohesive, inclusive movement dedicated to a democratic and multiethnic state.

But those fighting the Assad government range wildly in political and ethnic beliefs, and not all are interested in Western support.

The conflict has killed more than 100,000 people and ripped apart the delicate sectarian fabric of Syrian society. Al Qaeda-linked rebels and other extremist groups have been responsible for some of the same types of massacres and ethnic attacks that the Assad regime has committed.

Gen. Dempsey said Syria’s war was “tragic and complex”.

“It is a deeply rooted, long-term conflict among multiple factions, and violent struggles for power will continue after Assad’s rule ends,” he wrote. “We should evaluate the effectiveness of limited military options in this context.”

Despite calling for Mr Assad to leave power in 2011, President Barack Obama has refused to allow the US to be drawn directly into the conflict. Officials have said, however, that the US is prepared to provide lethal aid to moderate units among the opposition ranks. It’s unclear what, if any, weapons have been delivered so far.

In the past, Gen. Dempsey has said that the establishment of a no-fly zone to protect the Syrian rebels would require hundreds of US aircraft at a cost as much as $1 billion a month, with no assurance that it would change the war’s momentum.

He also discouraged options such as training vetted rebel groups, limited strikes on Syria’s air defenses and creating a buffer zone for the opposition. He stressed the need to avoid an outcome similar to Iraq or Afghanistan by preserving a functioning state for any future power transfer. And he cited risks such as lost US aircraft.

Representative Engel, who wants more forceful US action, has proposed the use of cruise missiles and other weapons against Syrian government-controlled air bases. The congressman said such strikes would ground Mr Assad’s air force and reduce the flow of weapons to his government from Iran and Russia, while requiring no American troops on the ground in Syria or in its airspace.

General Dempsey said this approach wouldn’t tip the balance against Mr Assad and wouldn’t solve the deeper problems plaguing Syria.

“We can destroy the Syrian air force,” he said. “The loss of Assad’s air force would negate his ability to attack opposition forces from the air, but it would also escalate and potentially further commit the United States to the conflict.”

Instead, General Dempsey spoke in favour of an expansion of the Obama administration’s current policy.

The US can provide far greater humanitarian assistance and, if asked, do more to bolster a moderate opposition in Syria. Such an approach “represents the best framework for an effective US strategy toward Syria,” General Dempsey said.

Telegraph