Kuomintang chairwoman Cheng Li-wun's trip comes two months after her "peace" visit to Beijing, where she met Chinese President Xi Jinping -- the first such meeting in a decade -- and weeks after US President Donald Trump's summit with Xi in the Chinese capital.

It also comes after the KMT recently thwarted the Taiwanese government's plan to spend nearly $40 billion on critical weapons, including US arms and domestically produced drones.

Speaking to reporters before leaving for the United States -- Taiwan's most important security backer -- Cheng said she hopes her party can play a key role in regional peace efforts and "gain deeper trust from the US".

"Only the KMT is truly serious and responsible in taking on the most important role of maintaining peace and stability across the Taiwan Strait," Cheng told a press conference.

Cheng has rocked Taiwanese politics since her unexpected rise to the top of the party last year and drawn criticism for being too pro-China.

The KMT has long advocated closer relations with China, which claims Taiwan is part of its territory and has threatened to use force to seize it.

But Cheng's cross-strait rhetoric has gone beyond the comfort zone of many people in her own party and caused unease among foreign partners, including Washington.

- 'Sharper questions' -

Over the next two weeks, Cheng will visit San Francisco, Boston, New York, Washington and Los Angeles. She plans to meet with US lawmakers, government officials, think tanks and supporters, according to her itinerary.

Cheng said she would be "very willing" to meet Trump, which is seen as unlikely. US protocol has previously limited Taiwanese opposition leaders to meeting lower level officials.

Analysts told AFP that US government officials and lawmakers are likely to interrogate Cheng on the KMT's position on China and its decision to slash the government's special defence budget.

While Taiwan has its own defence industry, it remains heavily reliant on the United States for weapons to deter a potential attack by China.

But there are concerns in Taipei over Washington's commitment after Trump recently suggested arms sales to the island could be a bargaining chip with China.

Compared with her trip to China, Cheng can expect "far less pomp and far sharper questions" in the United States, said Ryan Hass, an expert on China and Taiwan at the Washington-based Brookings Institution.

"Her challenge will be to persuade Washington that the KMT's engagement with China can coexist with strong deterrence," Hass wrote in a recent opinion piece in the Taipei Times newspaper.

Jason Hsu, senior fellow at the Hudson Institute think tank and former KMT lawmaker, said Cheng will face "a lot of serious questioning from the administration and Congress for KMT's leaning toward Beijing".

The KMT and Taiwan People's Party, which together control parliament, recently passed a $25 billion defence spending bill limited to US weapons.

It excluded the procurement of drones made in Taiwan, which the government has said is critical for developing domestic production capacity to sustain its forces during a war.