China reiterated its threat to use force against those attempting to separate Taiwan from Beijing, state-run media reported on Thursday.
The comments by China's ambassador to the US, Qin Gang, came after unconfirmed reports of US House Speaker Nancy Pelosi planning a visit to Taiwan in August.
Qin said if anyone challenges China's sovereignty and territorial integrity, his country will take forceful measures to firmly safeguard national sovereignty and territorial integrity, according to the daily Global Times.
"If anyone tries to separate Taiwan from China, if anyone wants to challenge China's bottom line, the Chinese military will take forceful measures to firmly safeguard national sovereignty and territorial integrity," the daily quoted Qin as saying.
The US House speaker was scheduled to visit Taipei in April, but the trip was canceled when she contracted COVID-19.
The Chinese envoy, without naming anyone, said separatist forces and their activities pose the greatest threat to peace and stability along the Taiwan Strait.
China has already warned the US against Pelosi's expected visit, and the Defense Ministry has said if Washington interferes, the Chinese military will take strong measures to thwart any external interference and efforts for Taiwanese independence.
Beijing, which considers Taiwan a breakaway province, stated at the time that such actions could cause "serious damage to the foundation of China-US relations."
Wang Yi, China’s top diplomat, called the planned visit a “malicious provocation.”
If Pelosi goes ahead with the plan, she will be the first sitting US House speaker to visit Taiwan in 25 years, following Republican Newt Gingrich's 1997 trip to meet with then-President Lee Teng-hui.
Taipei has insisted on its independence since 1949 and enjoys diplomatic relations with at least 14 countries.
Interactions between Washington and Taipei have grown significantly since the tenure of former US President Donald Trump, with former and sitting lawmakers making trips to the island home to over 25 million people.
The US formally recognized China in 1979 and shifted diplomatic relations from Taipei to Beijing, including Taiwan as part of mainland China.
The Taiwan Relations Act, enacted in 1979, has governed US relations with Taiwan. Bilateral agreements known as the Three Communiques have also influenced ties.