The figure falls well short of the government's proposed budget of nearly US$40 billion for critical defence purchases, which includes US arms as well as Taiwan-made drones and other weapons.

Taiwanese lawmakers have been at loggerheads over how much to spend on improving defence capabilities against a potential attack by China, which claims the island is part of its territory and has threatened to forcibly seize it.

The Kuomintang (KMT), Taiwan's biggest opposition party which favours closer ties with China, and the Taiwan People's Party (TPP), said they would be willing to support NT$780 billion (nearly US$25 billion) in spending on US arms.

The KMT and the TPP control Taiwan's 113-seat parliament.

President Lai Ching-te's government has proposed spending NT$1.25 trillion on defence purchases.

The special funds would be spread out over eight years and would be in addition to normal defence spending that is included in the government's annual budget.

Months of fighting have left the KMT deeply divided, with the party's chairperson Cheng Li-wun -- who has drawn criticism from inside and outside the KMT for being too pro-China -- pushing for the allocation of NT$380 billion for US weapons, with the option for more acquisitions.

As pressure from the United States -- Taiwan's most important security backer -- mounted, however, senior KMT lawmakers demanded a much higher budget than the one initially proposed by the party.

Taiwan's parliament, which could vote on the proposal as early as Friday, previously gave the government a green light to sign US agreements for four weapons deals, even though funding for these and other arms had not yet been approved.

The weapons -- M109A7 self-propelled howitzers, Javelin anti-armor missiles, TOW 2B missiles and High Mobility Artillery Rocket Systems (HIMARS) -- account for nearly US$9 billion of the US$11.1 billion arms package announced by Washington in December.

The KMT was "willing to fully support" a second phase of arms sales worth more than US$15 billion that the defence ministry has told lawmakers would include "Patriot missiles, Hellfire (missiles), and related counter-drone defence systems", party caucus leader Fu Kun-chi told a press conference.

The announcement comes days before US President Donald Trump is due to arrive in Beijing for a summit with his Chinese counterpart Xi Jinping, who has warned the US against sending more weapons to Taiwan.

Cheng recently went to China, where she met with Xi, and she has expressed hopes to travel to the United States in June.