KATHMANDU (REUTERS) - Nepal has asked foreign airlines not to land heavily-loaded wide-body aircraft at the Himalayan nation's international airport, aviation authorities said on Friday, after potholes were found on the runway before the annual influx of mountain-going tourists.

More than two dozen foreign airlines operate regular flights from Asia and the Middle East to Nepal, home to eight of the world's 14 highest mountains, including Mount Everest. Six airlines fly wide-body planes into the capital, Kathmandu.

Ratish Chandra Lal Suman, head of the state-owned Civil Aviation Authority of Nepal, said a request had been sent to all foreign airlines to switch to narrow-body aircraft or to reduce payloads as authorities filled the holes.

It was not immediately clear how long it would take to eliminate the potholes, discovered last week.

The airline industry said the request was not mandatory and would be difficult to comply with.

"It is not a binding order to the airlines," said Mr Saroj Kumar Kasaju, chairman of the Board of Airlines Representatives Nepal, a body of airlines operating flights to Kathmandu.

He said airlines had already booked passengers and issued tickets as the peak tourism season begins in September.

"It will, therefore, be difficult to off-load passengers now," he said.

Tourism accounts for some 30 per cent of foreign currency earnings.

Kathmandu sits in a bowl surrounded by forested, rugged hills. Its airport is known as a tricky landing spot requiring a a steep descent.

A propeller-driven Dornier aircraft, headed to Lukla, the gateway to Mount Everest, crashed minutes after take off from Kathmandu last September, killing 19 people and highlighting concerns about air safety.