Speaker of the US House of Representatives Nancy Pelosi is scheduled to visit Taiwan on Tuesday, according to three sources briefed on the situation who spoke to CNBC. This is despite mounting Chinese threats that have Taiwan on high alert.

Taiwanese officials informed CNN that Pelosi will likely spend the night in Taiwan, although it is still unknown when she will arrive in Taipei.

According to Taiwanese media outlet The Liberty Times, Pelosi is also slated to attend Taiwan's parliament on Wednesday morning before continuing her Asia trip. The Taiwanese foreign ministry declined to comment on rumors regarding Pelosi's vacation intentions.

According to local sources, Taiwanese defense officials have canceled the leave of specific soldiers and commanders "to immediately prepare" for the possibility of war in response to House Speaker Nancy Pelosi's trip to Asia this week.

People's Liberation Army

The Chinese People's Liberation Army (PLA) will "not sit idly by" if Pelosi follows through with her scheduled visit, warned Chinese foreign ministry Spokesperson Zhao Lijian during a Monday briefing.

Zhao noted that because of Pelosi's position as the "No. 3 official of the US government," travel to Taiwan, over which China claims sovereignty, would have "lead to egregious political impact."

"We want to remind the United States that China is ready and that the Chinese People's Liberation Army will never remain inactive. When asked about the repercussions of Pelosi heading a congressional delegation to Taiwan, Zhao told reporters, "China will take firm responses and strong countermeasures to defend its sovereignty and territorial integrity."

"As for what measures, if she dares to go, then let's wait and see," Zhao continued.

The PLA posted a video mimicking a missile strike, aircraft carriers moving, and fighter fighters in formation on social media before Nancy Pelosi's anticipated trip to Taiwan.

The video, shared on WeChat on Monday morning, followed Chinese claims that they could shoot down the US House Speaker's plane and unleash a military reaction if she arrived in Taipei on Tuesday night.

According to Xinhua, the Chinese military conducted "live-fire exercises" near the Pingtan islands off Fujian province before the PLA's foundation anniversary on Monday. The Maritime Safety Administration issued a warning for vessels to avoid the area.

Hu Xijin, a prominent figure in Chinese official media, also delivered a solid warning to Pelosi: "Let her go to Taiwan. But before leaving, she should pray, wishing herself safe travel and not to be remembered by history as the sinner who triggered the escalation process that led to a large-scale war in the Taiwan Strait.

US preparations

According to a US statement, the US Defense Department is working to ensure around-the-clock monitoring of Chinese movements in the region during the House Speaker's trip to Asia. US officials, particularly in the US military, had warned about the trip due to safety concerns amid high tensions with China.

Antony Blinken, the US secretary of state, also told reporters on Monday that the speaker "will make her own decision about whether or not to visit Taiwan," emphasizing the independence of Congress from the White House.

"Congress is an autonomous, co-equal branch of government; the decision is solely the speaker's responsibility. This has precedent because a former speaker has traveled to Taiwan. Blinken stated, alluding to Newt Gingrich's travel to Taiwan in 1997, that many members of Congress visit Taiwan, including this year.

Blinken added, "Should she decide to visit, we expect China to act responsibly and refrain from engaging in escalation going forward."

The itinerary for Pelosi's trip was announced over the weekend and included trips to Singapore, Malaysia, South Korea, and Japan. Rapid speculation arose as to whether or not the speaker of the House would visit Taiwan, prompting Chinese media leaders to threaten "severe punishment."