Kabul: The first American soldiers of about 10,000 due to leave Afghanistan this year have flown home, military officials said on Friday, kicking off a gradual drawdown due to be completed in 2014.

US President Barack Obama in June announced that 33,000 American troops would leave Afghanistan by the end of next summer, leaving behind 65,000 and effectively ending a military surge ordered into the country late 2009.

Around 650 US army troops deployed northwest of the capital in the province of Parwan flew out on Wednesday and will not be replaced by an incoming unit, the US military confirmed on Friday.

"It's correct that these soldiers are the first to redeploy from Afghanistan without being replaced by a new rotation of soldiers since the president's announcement," said US army press Officer Major Michael Wunn.

US officers have said that a total of about 800 soldiers in two Army units will depart this month.

The speed of the drawdown has been heavily criticized in Washington -- liberals wanted more, Republican hawks complained it was too fast and top Pentagon officials felt snubbed for having much of their advice overruled.

The troops who left on Wednesday were from the Iowa National Guard's 1st Squadron, 113rd Cavalry Regiment and their duties will be taken on by others already in the country.

Another contingent of military trainers from 1st Squadron, 134th Cavalry Regiment who had been working in Kabul will leave later this month and their job given to Afghan security forces, the military said.