The US Congress last month approved a draft revision of an arms sales authorisation bill that could clear the way for Taiwan to acquire a more powerful version of the fighter from the US.

But military officials said that in the meantime, Taiwan must seek to upgrade the combat performance of its existing fleet. Taiwan now operates 145 F-16 A/B - single or two-seater - jets. The A/B model was the first variation sold out of the US in the mid-1980s and was followed by the C/D version, with better air to air missiles, and all-weather capability due to improved radar.

'The government of President Ma Ying-jeou has repeatedly asked to purchase the C/D jets, but so far the United States has only agreed to help retrofit our A/B fighter jets,' Luo said.

He said that before Taiwan acquired more advanced fighter jets, the retrofit was in line with the air force's current needs.

The Pentagon offered in September to retrofit the A/B jets with new technology and equipment, including active electronically scanned array (AESA) radar, AIM-9X Sidewinder air-to-air missiles and joint direct attack munition (JDAM) guidance kits, which turn unaided bombs into 'smart' ones.

The proposed deal has irked the mainland, which summoned the US ambassador and warned it would affect ties between Beijing and Washington.

Air force officials said the US submitted the offer letter to Taiwan in May and the air force had finished reviewing it. Final approval rests with the Defence Ministry.