Nancy Pelosi, Speaker of the US House of Representatives, plans to meet Taiwan’s president Tsai Ing-wen on Wednesday, in a controversial visit that has triggered concern about a possible military response from China.

Three people familiar with the situation said Pelosi would meet Tsai in Taipei as part of a wider visit to Asia that began in Singapore on Sunday.

Pelosi did not include Taiwan on her official itinerary — which includes Japan, South Korea and Malaysia — over security concerns, but the Financial Times first reported that she would be the first Speaker to visit Taiwan in 25 years.

China has issued strong warnings to the Biden administration, including suggestions that the People’s Liberation Army could take action if the 82-year-old Democrat went ahead with her planned visit.

US secretary of state Antony Blinken on Monday urged China to act responsibly and “not to engage in any escalation” if Pelosi visits Taiwan.

President Joe Biden dispatched senior officials, including national security adviser Jake Sullivan, to lay out the risks to Pelosi, but people familiar with the situation said she had decided to press ahead with the landmark trip.

Many Republicans, and a few Democrats, have urged Pelosi to proceed, arguing that any decision to postpone or cancel would be capitulating to China.

But the White House is worried that it could trigger a crisis across the Taiwan Strait, where tensions have spiked over the past year.

On Monday China intensified its threats.

After the People’s Liberation Army conducted live-fire drills on Pingtan, an island in the Taiwan Strait, and other drills in the South China Sea last week, the China Maritime Safety Administration said there would be more exercises from Tuesday to Saturday.

“The Chinese People’s Liberation Army will not sit back,” China’s foreign minister spokesperson Zhao Lijian said on Monday.

At the White House on Monday, John Kirby, the National Security Council communications head, said there was “no reason” for Beijing to turn a potential visit into a “pretext to increase aggressive military activity”.

“China appears to be positioning itself to potentially take further steps in the coming days,” Kirby said.

“These potential steps . . .could include military provocations, such as firing missiles in the Taiwan Strait.” Kirby repeatedly declined to confirm that Pelosi would visit Taiwan during a press briefing but said: “We’re going to watch this very, very closely.

We’re going to make sure that she has a safe and secure visit.” A longtime critic of China, particularly over human rights, Pelosi would be the most senior lawmaker to visit Taiwan since then Speaker Newt Gingrich went in 1997.

Beijing opposes all visits by US lawmakers to Taiwan, over which it claims sovereignty.

But it is particularly sensitive to Pelosi’s visit because she is second in succession to the presidency after the vice-president, and belongs to the same party as Biden.

Her visit will also come just months ahead of the Chinese Communist party’s 20th Congress, at which president Xi Jinping is expected to receive an unprecedented third term as leader.

Beijing has accused the US of diluting the “one China” policy, under which Washington recognises Beijing as the sole government of China while acknowledging, but not endorsing, its stance that Taiwan is part of China.

The US military has been preparing to protect Pelosi, who is flying on a US Air Force aircraft.

Few experts believe China would try to shoot down her aircraft, but Chinese fighter jets could attempt to intercept her plane.

This could trigger a dangerous situation because the US military would be compelled to intervene to protect Pelosi and her delegation.

“If there’s a decision made that Speaker Pelosi or anyone else is going to travel and they ask for military support, we will do what is necessary to ensure a safe conduct of their visit,” General Mark Milley, chairman of the joint chiefs, said last week in response to a question from the FT.

One senior Taiwanese official said Taipei had not seen a marked increase in PLA activity over the past week, but China’s military had stepped up its movements around Taiwan in previous weeks.

“They have been raising the pressure a lot recently,” said a second senior Taiwanese official.

“They are sending both larger numbers of aircraft and ships and getting closer.” According to Taiwanese government data, on July 24 the PLA conducted joint air and sea manoeuvres on three sides around Taiwan, including an attack drone and a destroyer off its east coast, an anti-submarine warfare aircraft, and two fighter jets and a reconnaissance plane flying an incursion into the south-western edge of its “air defence identification zone”.

The day after those movements — some of which have not been made public — Japan’s military said another type of Chinese attack drone had flown between Yonaguni, a Japanese island near Taiwan’s east coast.

Data published by Japan’s military and Taiwan’s defence ministry also show that the PLA has stepped up activity around the southernmost islands of Japan and in Taiwan’s ADIZ since the second half of June.