The NATO force said it had withdrawn the several choppers and planes it dedicated to the search over the weekend and instead told its crew routinely flying over Afghanistan to look out for the chopper as an "additional task".

"Where possible we are going to follow the same flight path (as the chopper) and keep an eye out for it," spokesman Andy Elmes told AFP.

"The focused search that we carried out for two days -- we are not able to keep that up any more... we have to get on with our operations."

The US-led coalition based in insurgency-hit Afghanistan for four years had also despatched aircraft to look for the missing chopper on Sunday. A spokesman could not immediately say if it had resumed its search Monday.

The chopper last made contact with air traffic controllers as it was about to leave Pakistani air space on Friday to fly over Afghanistan on the way to its home base in Turkmenistan, the International Committee of the Red Cross said.

The aircraft, chartered by the ICRC after the October 8 earthquake that killed thousands of Pakistanis, had been due to refuel in Afghanistan.

A search on the Pakistan side of the border continued Monday, Red Cross spokesman James Reynolds said in Islamabad.

"The search operation is continuing... on the Pakistan side of the border. Unfortunately, we have no further information," he said.

Pakistani military spokesman Brigadier Shahjahan Ali Khan said Sunday the helicopter might have come down on the rugged Afghan border.

"The helicopter might have crashed astride the border. It is our guess, we have no clue so far," he told AFP.

The Mi-8 transport chopper left the Pakistani city of Peshawar on Friday with seven crew members from Turkmenistan but no Red Cross staff.

It was one of several international aircraft that provided essential rescue and relief help after the earthquake that killed more than 73,000 people in mountainous northwestern Pakistan and Pakistani Kashmir.

About 3.5 million others lost their homes and the United Nations has warned that hundreds of thousands of people living in tents are at risk of falling ill during the bitter Himalayan winter.

Six Pakistani soldiers were killed when a Pakistan army Mi-17 helicopter crashed during relief operations in Kashmir on October 16.

More than a dozen helicopters operating under NATO and coalition deployments in rugged Afghanistan have crashed or been shot down by insurgents since the ousting of the Taliban regime in 2001.

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