The $8 billion deal for 66 warplanes was approved during US President Donald Trump's first term in the White House, with delivery scheduled for 2026.

Speaking in parliament, Air Force Chief of Staff Lee Ching-jan said flight tests of the new fighters would be carried out "earlier" than planned this month.

"For now, 54 aircraft have entered the assembly line, compared with 50 in October. The progress is being accelerated," Lee said.

Defence Minister Wellington Koo said last month that Lockheed Martin, the US defence contractor building the jets, had ramped up production, running two shifts every weekday.

"There are 50 aircraft on the assembly line at the same time, and some airframes have already completed structural assembly," Koo said.

But Koo said it would be "challenging" for all the aircraft to be delivered in 2026.

Taiwan is seeking to strengthen its defences to deter China, which claims the democratic island is part of its territory and has threatened to use force to annex it.

The F-16V -- a fourth-generation multi-role fighter -- is a significantly upgraded version of Taiwan's ageing F-16 A/B jets. Taiwan completed upgrades of 141 older F-16s to the V standard in late 2023.

The United States does not have formal diplomatic relations with Taiwan, but Washington remains Taipei's most important backer and biggest arms supplier.

It has sold billions of dollars in weapons to Taiwan -- including fighter jets, missiles, and warships -- as part of its commitment to help the island maintain sufficient self-defence capabilities.