Nancy Pelosi touched down in Taiwan for the first visit by a U.S. House speaker to the self-ruled island since Newt Gingrich in 1997.

Gingrich, a Republican, is warning China not to follow through on some of the most extreme threats — which have included calls from a state-affiliated commentator to shoot down any U.S. military aircraft flying to Taiwan.

"That would be literally an act of war, and we would have no choice except to retaliate massively," Gingrich said Monday on Fox News.

But the former speaker acknowledged that an actual clash stemming from Pelosi's planned visit from China — which claims Taiwan as its own and has vowed to one day unify the island with the mainland — is unlikely.

China's threats are largely "bluff," Gingrich said.

They're also nothing new: When he led a congressional delegation to Taiwan a quarter-century ago, Gingrich said he heard similar complaints from officials in Beijing. "They're not going to take on the United States, they're not going to take on the speaker of the House and all these various threats are … not going to happen," Gingrich said on Fox.

The White House said it is prepared for China to take a range of retaliatory measures in response to Pelosi's visit that could include firing missiles around Taiwan, staging large-scale military exercises in the region or making public statements about Taiwan's status that go beyond the norm. And the island is on high alert for a show of force from Beijing.

Pelosi arrived in Taiwan on Tuesday night, local time, for an unscheduled but highly anticipated stop as part of a congressional delegation to Asia.

The White House — concerned the visit could spark a crisis in the Taiwan Strait — publicly warned the trip wasn't a good idea, although it maintained that she had a right to go.

Yet some Republican lawmakers had urged Pelosi to go, arguing that changing course would send a signal to Beijing that threats could influence American foreign policy.

"She has to go to Taiwan," Gingrich told Fox's Sean Hannity Monday. "To back down now would encourage every aggressive, bullying attitude" from officials in Beijing, he added, and could convince them they could get away with "trying to occupy Taiwan."

While Chinese officials were also unhappy about Gingrich's visit, the balance of powers between Beijing and Washington is different today. Pelosi faces a more powerful and assertive China, with a significantly stronger economy today than decades ago. China's president, who has not ruled out the use of force to unite Taiwan with the mainland, has said the question of the island's status "should not be passed down generation after generation."

Still, when Gingrich was there, relations between Washington and Beijing were already in crisis over the island's status: After Taiwan's president gave a speech in 1995 at Cornell University, his alma mater in New York, China fired unarmed missiles into the sea near Taiwan in 1996, and held military exercises in the Taiwan Strait. President Bill Clinton then sent two aircraft carriers and more than a dozen warships to the region.

The next year, Gingrich was invited to speak in Shanghai and Beijing, he said, and told Chinese authorities he would come — but also visit Taiwan. "They went crazy, and said, 'Oh, you can't do it,'" Gingrich told Fox News. "We said to them, 'Look, if you feel that strongly, we're going to skip China and go just to Taiwan.' "

The former speaker settled on a "compromise," he said, which was to fly to Taiwan from Japan and not directly from China.

While in China, Gingrich told Chinese Communist Party leaders that the United States "will defend Taiwan. Period." China's Foreign Ministry called the remark "indiscreet," and the White House said Gingrich was "speaking for himself," as The Post reported at the time.

Pelosi's visit represents a test for Taiwan as it continues to seek more international recognition amid efforts by China to isolate it on the global stage. Like Gingrich, Pelosi had to walk a fine line in the lead-up to her trip, supporting Taiwan but never appearing to endorse its independence — a red line for Beijing. In a news conference in late July, she said that "none of us has ever said we're for independence when it comes to Taiwan. That's up to Taiwan to decide."

President Joe Biden made it clear in conversations with Chinese officials "that Congress is an independent branch of government and Speaker Pelosi makes her own decisions," said John Kirby, spokesman for the National Security Council.

China should "see this for exactly what it is: nothing new," Kirby added during a news conference. "No change to our policy and certainly not an unprecedented visit by the Speaker of the House."

China's Ministry of Defense said that the Chinese People's Liberation Army (PLA) would "not sit idly by" should Pelosi visit Taiwan.

But some of its most inflammatory threats have not come from government officials. On Friday, a Chinese journalist issued what appeared to be a direct threat against Pelosi.

"If US fighter jets escort Pelosi's plane into Taiwan, it is invasion," Hu Xijin, the former editor in chief of the Chinese state-run outlet Global Times, said in a tweet that has since been deleted for violating the platform's rules.

"The PLA has the right to forcibly dispel Pelosi's plane and the US fighter jets, including firing warning shots and making tactical movement of obstruction. If ineffective, then shoot them down," he added.