It said the F-35 was under consideration as a replacement for Singapore's F-5 fighters, which are nearing the end of their operational life, and F-16s, which are at their "midway mark".

Defence Minister Ng Eng Hen told parliament on Monday that the wealthy city-state was also looking to replace its submarine fleet as part of plans to further improve its military, already the best equipped in Southeast Asia.

"Though the F-35 is still in development, we are nonetheless interested in the platform for our future needs," Ng said during a debate on the national budget.

"For the longer term, the RSAF (Republic of Singapore Air Force) has identified the F-35 as a suitable aircraft to further modernise our fighter fleet. We are now in the final stages of evaluating the F-35," he said.

The single-engine fighter, which has advanced software and stealth capability, is being developed under a programme led by the United States, with eight countries helping to fund the aircraft.

Since the contract was awarded to US aerospace giant Lockheed Martin in 2001, the cost has skyrocketed and the project has been plagued with delays.

In the latest glitch, the US military last month suspended all test flights over potential engine problems after a crack was discovered on a turbine blade in one F-35 engine.

However, the Pentagon's director of the F-35 programme, Lieutenant General Christopher Bogdan, dismissed any talk of foreign customers backing out.

Singapore's defence ministry "will have to be satisfied that this state-of-the-art multi-role fighter meets our long-term needs, is on track to be operationally capable, and most importantly, is a cost-effective platform," Ng said.

He said Singapore was also aiming to replace its ageing Challenger class submarines which it acquired as refurbished units from Sweden in the 1990s.