Afghanistan's fledgling air force is more like a bicycle than a modern fighting machine, its commander has said, pleading for advanced aircraft to fight the Taliban as US-led NATO forces prepare to withdraw.

Air power is crucial in the rugged country where a poor road network is often mined by insurgents, and the Afghan government is pressing hard for the US to boost its air capability before it pulls out next year.

"We will face huge and complicated challenges if the Americans do not provide us with these planes," Major General Abdul Wahab Wardak told AFP, listing a range of attack and transport aircraft he says Afghanistan needs.

In Washington on Tuesday President Barack Obama announced that 34,000 US troops will withdraw from the country by the end of 2013, with the remaining half leaving by the end of 2014, taking with them their far superior firepower.

For the past 11 years NATO's vast fleet of fighter jets, attack helicopters, unmanned drones and transport aircraft have supported ground troops in operations against the Taliban.

Last year coalition aircraft in Afghanistan flew 28,640 close air support sorties, firing weapons 4,082 times, according to official figures. Drones fired 494 times.

They also flew tens of thousands of surveillance sorties and flights carrying troops and cargo.

The US is negotiating leaving a small residual force in Afghanistan after 2014, but the overwhelming air power will all but disappear.

As part of its exit strategy Washington is helping rebuild the Afghan Air Force (AAF) -- which currently has no fixed-wing attack planes -- but the government has complained that the process is too slow.

The air force chief, a stocky former MIG-21 fighter pilot under Soviet occupation in the 1980s, harks back to the old days when the Afghan air force was a regional power to be reckoned with.

"To clarify the comparison of the air force we had in the past with now, I will give you this example," he said.

"Back then it was as if you were riding an armoured vehicle. Today it is as if you are riding a bicycle."

The air force of old disappeared in clouds of smoke during the civil war that followed the withdrawal of the Soviets in 1989, after 10 years of occupation.

"There was disunity among us, we started fighting each other, we fought among ourselves and destroyed our air force," Wardak said.

"But we have learned, we know we need unity to build the military and the country."

The words are spoken in Wardak's office in a large, US-funded air force compound adjacent to Kabul's international airport, but like many new things in Afghanistan it is more chimera than substance.

"We have lots of pilots, but no planes," an officer confided ahead of the interview.

Operational aircraft currently in use by the AAF include 43 helicopters -- mainly Russian Mi-17 transports plus six Mi-35 gunships -- a spokeswoman for NATO's air training command in Kabul said.

The air force also has fixed-wing transports including 16 Italian C-27s, but they were grounded for several months last year and are to be withdrawn from service.

"The US has promised to give us four C-130s (large transporters), and also promised to give 20 AT-6 (light attack aircraft)," Wardak said.

The US Air Force (USAF) announced last year that it was reopening a contest for a contract to build 20 light attack aircraft for Afghanistan after the cancellation of an award to Brazil's Embraer.

A final decision on the contract has not been announced, though the first planes are expected to be delivered in the second half of 2014.

"The Air Force is working to fill the request from the Afghan Ministry of Defense for four C-130Hs," USAF spokesman Ed Gulick told AFP.

"Additionally, the USAF is working source selection for a light air support (LAS) aircraft for the Afghan Air Force."

The C-27 transporters, also known as G222s, were expected to serve as the AAF medium airlift aircraft for up to 10 years after the first one was delivered in 2009.

But "aircraft and contract performance limitations have caused the USG to pursue the G222's replacement system at a much more rapid pace", Gulick said.

"The date flying operations will cease is yet to be determined."

President Hamid Karzai told a news conference last month the US had also agreed to provide drones for intelligence gathering, but the move has not been confirmed.

Wardak said that to defend itself against regional threats in one of the world's most unstable areas, the country also needs fighter jets, along with anti-aircraft and radar systems.

NATO and Western governments, keen to exit a conflict increasingly unpopular at home, constantly talk up the capability of the Afghan security forces to take on the fight alone.

But Afghan soldiers and police are already dying at five times the rate of NATO forces and without air support will be even more vulnerable.