(Corrects description of defence spending in paragraph 4 to percentage of economic output, not percentage of budget)

By Michael Martina, Yimou Lee and Ben Blanchard

WASHINGTON/TAIPEI (Reuters) -The United States plans to ramp up weapons sales to Taipei to a level exceeding President Donald Trump's first term as part of an effort to deter China as it intensifies military pressure on the democratic island, according to two U.S. officials.

If U.S. arms sales to Taiwan do accelerate, it could ease worries about the extent of Trump's commitment to the island. It would also add new friction to the tense U.S.-China relationship.

The U.S. officials, who spoke on condition of anonymity, said they expect U.S. approvals for weapons sales to Taipei over the next four years to surpass those in Trump's first term, with one of the officials saying arms sales notifications to Taiwan could "easily exceed" that earlier period.

They also said the United States is pressing members of Taiwan's opposition parties not to oppose the government's efforts to increase defense spending to 3% of the island's economic output.

The first Trump administration approved sales of approximately $18.3 billion worth of weapons to Taiwan, compared with around $8.4 billion during Joe Biden's term, according to Reuters calculations.

The United States is Taiwan's most important international backer and arms supplier despite the lack of formal diplomatic ties between Washington and Taipei. 

Even so, many in Taiwan, which China claims as its own, worry that Trump may not be as committed to the island as past U.S. presidents.

On the election campaign trail, Trump suggested Taiwan should pay to be protected and also accused the island of stealing American semiconductor business, causing alarm in Taipei.

China has vowed to "reunify" with the separately governed island, by force if necessary. Taiwan's government rejects Beijing's sovereignty claims, saying only the island's people can decide their future.

The U.S. officials said administration officials and Trump himself were committed to "enhancing hard deterrence" for Taiwan. 

"That's where the president is. That's where all of us are," one U.S. official said, adding that they were working closely with Taiwan on an arms procurement package to be rolled out when Taiwan secured domestic funding. 

Taiwan's Presidential Office told Reuters the government is determined to strengthen its self-defense capabilities and pointed to its proposals to increase defense spending.

"Taiwan aims to enhance military deterrence while continuing to deepen its security cooperation with the United States," Presidential Office spokesperson Wen Lii said.

Taiwan's defense ministry declined to comment on any new arms sales, but reiterated previous remarks by the island's defense minister, Wellington Koo, about the importance of "solidarity and cooperation of democratic allies."

'DON'T GET IN THE WAY'

Taiwan's President Lai Ching-te and his Democratic Progressive Party (DPP) aim to increase defense spending to 3% of GDP this year through a special defense budget.

But the island's parliament, controlled by opposition parties the Kuomintang (KMT) and the Taiwan People's Party (TPP), passed budget cuts earlier this year that threatened to hit defense spending. 

That triggered concerns in Washington, where officials and lawmakers have regularly said the U.S. cannot show more urgency over Taiwan's defense than the island itself.

"We're messaging pretty hard (in Taipei) to the opposition. Don't get in the way of this. This isn't a Taiwanese partisan question. This is a Taiwanese survival question," one of the U.S. officials told Reuters.

Three people in Taiwan with direct knowledge of the situation confirmed that the U.S. government and U.S. congressional visitors have been pressing the opposition parties in Taiwan not to block defense spending, especially the coming special defense budget, which is expected to be proposed to parliament later this year.

"As long as they knew there were people from the opposition in the room, they directly asked them not to cut the defense budget," one of the people said.

Alexander Huang, director of the KMT's international department, told Reuters it was "beyond question" that the party firmly supports increasing the defense budget and its "doors are open" to the U.S. government and the ruling DPP for consultations.

"Supporting an increased budget does not mean serving as a rubber stamp, nor does it preclude making adjustments or engaging in negotiations regarding the special budget proposals put forth by the DPP administration," he added.

The much smaller TPP said it has "always had smooth communication with the U.S. side and has continued to engage in in-depth dialogue on issues such as national defense and regional security."

Reuters reported in February that Taiwan was exploring a multi-billion dollar arms purchase from the U.S., hoping to win support from the new Trump administration.

New weapons packages are expected to focus on missiles, munitions and drones, cost-effective means to help improve Taiwan's chances of rebuffing any military action by China's much larger forces.  

For years, China has been steadily ramping up its military pressure to assert its sovereignty claims over the island that is home to critical chip manufacturing vital to the global economy.

Separately, one of the U.S. officials said the Trump administration would not object to a transit this year through U.S. territory by Lai, whom Beijing labels a "separatist." 

Past visits to the United States by Taiwanese officials have triggered angry objections by China, which sees such trips as inappropriate given that the United States has diplomatic relations with Beijing, not Taipei.

Taiwan's presidential office spokesperson Lii said there are currently "no plans for a presidential transit through the United States at the moment."

(Reporting by Michael Martina and David Brunnstrom in Washington and Yimou Lee and Ben Blanchard in Taipei; Editing by Don Durfee, Daniel Wallis and Lincoln Feast.)