Taiwan calls itself a sovereign nation, but Beijing insists the democratic island is part of its territory and opposes any official exchanges with it.

Lai's office said he spoke to Johnson on Thursday morning Guam time, the most high-level US contact the Taiwanese leader has had during his Pacific tour.

A 2022 visit to Taiwan by then US House speaker Nancy Pelosi prompted China to launch military drills around the self-ruled island.

The president also had calls with Democratic Minority Leader Hakeem Jeffries and Senator Roger Wicker, the top Republican on the Armed Services Committee.

They "conveyed the strong bipartisan support of the US Congress in assisting Taiwan in defending democracy and freedom," the president's office said.

Like most countries, the United States does not have official diplomatic relations with Taiwan, but Washington is Taipei's most important backer and biggest supplier of arms.

Lai's Pacific trip, and in particular his US stops, have drawn a barrage of criticism from Beijing, which rejects any international recognition of Taiwan.

Beijing on Thursday urged the US to "stop sending wrong signals" following the Lai-Johnson call.

"We urge the United States to clearly recognise the serious danger that separatist acts of Taiwan independence pose to peace and security across the Taiwan Strait," a foreign ministry spokesman said.

- 'Rock solid partnership' -

During a two-day visit to the US state of Hawaii at the beginning of the tour, Lai discussed "China's military threats" towards Taiwan in a 20-minute call with Pelosi and met with US government officials and members of Congress.

Lai's week-long tour is aimed at shoring up international support for Taiwan as China maintains military pressure on the island and seeks to isolate it by poaching its few remaining allies and blocking it from global forums.

Lai arrived in Guam on Wednesday following visits to Pacific island nations Tuvalu and the Marshall Islands, after the stop in Hawaii.

Speaking at a banquet in the capital Hagatna on Thursday, Lai hailed the "deep connections" and "rock solid partnership" between Taiwan and the United States.

"Together, we are good partners in defending democracy, freedom and prosperity for both sides," Lai told an audience that included Guam Governor Lou Leon Guerrero.

Ingrid Larson, from the Washington office of the American Institute in Taiwan, which serves as a de facto US embassy to the island, also attended.

Lai also called on the world's democracies to "not bow down to authoritarian regimes" as he hailed Taiwan as "the beacon of democracy of Asia."

At the banquet, Larson said the United States would keep helping Taiwan "bolster its self-defense capabilities" and its "ability to protect itself against coercion".

- 'Sincerest gratitude' -

Lai also addressed the Guam parliament -- a first for a Taiwanese president, his office said -- before flying to the Pacific island nation of Palau, the final stop of his trip.

Extending his "sincerest gratitude" to lawmakers for supporting Taiwan's access to the international arena, Lai said Taiwan and Guam were "like family".

Palau, Tuvalu and the Marshall Islands are among 12 nations that still recognise Taiwan diplomatically, including the Vatican, after China convinced others to dump Taipei in favour of Beijing.

Lai's Pacific tour has sparked fury in China, which on Tuesday vowed to defend its "national sovereignty" and "territorial integrity".

China regularly deploys fighter jets and warships around the island to press its claims, and Beijing has not ruled out using force to bring the island under its control.

- Military drills -

In his first public speech of the trip on US soil, Lai said Saturday there was a need to "fight together to prevent war", warning there were "no winners" from conflict.

Lai's call with Johnson would have "positive implications" for Taiwan's ties with the incoming Trump administration, said Su Tzu-yun, a military expert at the Institute for National Defense and Security Research.

But analysts were divided on whether China would launch another round of military exercises around the island.

Lai's predecessor Tsai Ing-wen met then-US House speaker Kevin McCarthy in California in April 2023 during a Latin America trip, to which Beijing responded with military drills.

China also held large-scale exercises after Lai's inauguration in May and following his National Day speech on October 10.

"I believe the probability is relatively low because there's already fatigue from overusing such responses," said Li Da-jung, an international relations expert at Tamkang University.

Stephen Tan, a Taipei-based analyst on Taiwan-China relations, said drills were "likely", but their "intensity remains to be observed".