Sixteen Americans died in a series of helicopter crashes and Taleban attacks across Afghanistan in one of the bloodiest days since the 2001 invasion.

Ten people were killed and at least 26 wounded when a Chinook helicopter crashed in western Afghanistan yesterday during a pre-dawn battle with insurgents.

In Helmand province, in the south of the country, four soldiers were killed and two seriously wounded when two helicopters collided in mid-air, officials said. Two more soldiers died in separate incidents.The loss of life on Monday was the highest in a single day for US forces since 2005. It underlined the sense of crisis about the war in Washington, where President Obama chaired his sixth key Afghan strategy session yesterday in less than a month.

Mr Obama met seven of his most senior advisers in the White House Situation Room as reports emerged that he was leaning towards a hybrid strategy based on the successful troop surge used in Iraq two years ago, and that a decision could be announced before the run-off election planned for November 7th.

After the meeting Mr Obama flew to a Florida naval base where he paid tribute to the dead, saying: “They gave their lives to protect ours”. In the same speech he said that he would not hesitate to use force in defence of US interests nor rush his decision on Afghanistan.

The new strategy would combine an emphasis on the protection of civilians with a largely separate offensive against the militants using special forces and intelligence gleaned from an expanded effort to win hearts and minds in built-up areas. It would grant General Stanley McChrystal fewer than the 44,000 extra troops he has requested, although the option of a full-scale surge was still on the table, said officials speaking to The Wall Street Journal.

According to The Washington Post, Pentagon planners have conducted detailed war games based on two scenarios. In one 44,000 extra troops enable General McChrystal to triple the number of soldiers on the ground in the south, where the Taleban is strongest.

In another only 10,000 to 15,000 reinforcements are sent, allowing accelerated training of Afghan soldiers but no full-scale counter-insurgency. In both cases each extra US soldier would cost taxpayers $1million (£610,000) a year. Monday’s deadliest incident involved a Chinook cargo helicopter that came down under heavy fire soon after midnight as it tried to extract a US special forces team from a night raid on one of the region’s most wanted drug smugglers.

The operation was backed by a squad of Afghan commandos and civilian counter-narcotics agents.

“Seven US service members and three US civilians were killed,” a military spokesman said. At least 11 American troops were injured in the crash in Badghis province, as well as 14 Afghan soldiers and one American civilian.

The elite US troops had led an airborne assault against a compound in Darpum district believed to harbour insurgents linked to Afghanistan’s multibilliondollar opium trade, officials said. “During the operation insurgent forces engaged the joint force and more than a dozen enemy fighters were killed in the ensuing firefight,” the spokesman said.

Moments after the force boarded a Chinook to leave the battlefield, the aircraft crashed into the main bazaar.

A spokesman for the Taleban claimed responsibility. Qari Yousuf Ahmadi said: “There was fighting in the bazaar between foreign troops and the Taleban. During the fighting the Taleban shot down a foreign helicopter.”

A Nato spokesman said that the cause of the crash was still being investigated but it was not thought to have been enemy fire. Taleban fighters continued to attack the American-led force after the helicopter crashed, hampering efforts to evacuate them.

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