Qatar Airways stepped up its criticism of US engine maker Pratt & Whitney over delays and technical problems on Wednesday, saying that engines for its Airbus A320neo aircraft had not been adequately tested.

Qatar Airways has refused to take the jets because of engine glitches. Last month it threatened to switch to alternative engine supplier CFM International .

"I don't think this engine was tested adequately, especially for the temperatures in which Qatar Airways will operate," chief executive Akbar Al Baker said.

"We will only accept it when we are fully satisfied that it can operate efficiently and safely at Qatar operations (and) ... once we get sufficient performance guarantees and undertakings from both Airbus and Pratt & Whitney," he told a news conference at the ITB tourism exhibition in Berlin.

"We are at the threshold of the walk-away clause in our contract, but I hope we will not have to exercise this."

Pratt & Whitney had no immediate comment but has said it is on track to eliminate problems with slow engine start-up times and erroneous software messages by June.

Meanwhile, industry sources say that more than a dozen part-built A320neo jets are on the ground at Airbus headquarters in Toulouse waiting for their engines before they can be delivered.

While keeping up the pressure in public, people familiar with the matter say that Qatar Airways is expected to give the planemaker and its engine supplier more time to fix the problems.

"We're confident that with Pratt & Whitney's support we will address any early (lessons) and meet our targets," Airbus said.

OIL FACTOR

CEO Al Baker disclosed that the airline had earlier deferred delivery of four Airbus A380s by one year when oil prices were high, only to agree to take delivery now prices have dropped.

The company would consider exercising options for a further three jets if oil prices remain low, he said, though he warned that oil prices are a "double-edged sword" for airlines because premium traffic yields have slipped in the face of weaker business sentiment and a drop in spending by oil producers.

On the airline's international ties, Al Baker predicted deeper links with British Airways owner IAG, in which it holds a 10.08 percent stake.

Areas for possible cooperation include procurement, computer systems, fuel, insurance and even aircraft buying after a joint Boeing purchase with Emirates in 2013.

In Iran, he sees room for expansion after the lifting of sanctions that he said had been unfairly applied to the country's civil aircraft fleet -- an unusual statement from a senior Gulf state official amid rising tensions in the area.

"My country has very good relations with Iran and has ... always played a balancing role in the region," he said.

He dismissed warnings from some analysts that Iran's airspace would be dominated by foreign carriers, saying that "there is enough demand for everyone".

On a recent trade row with major US carriers, Al Baker taunted his airline's most vocal adversary by saying that a decision to fly to Atlanta would "rub salt in the wounds" of Delta Air Lines but denied it would cause the airline harm.

Atlanta-based Delta and others have said that Gulf carriers have received state support that contravenes Open Skies agreements, a charge denied by Gulf airlines. – Reuters