Taiwan has applied to join the Comprehensive and Progressive Agreement for Trans-Pacific Partnership (CPTPP), a week after China submitted its own application.
The CPTPP currently has 11 members that represent about $13.5 trillion in GDP, or 13.4% of global GDP, making it one of the largest trade pacts in the world.
Japan, a CPTPP member, has been in close communication with Taiwan and welcomed its application into the trade pact, Taiwan's Ministry of Foreign Affairs said in a statement.
In a separate statement, Taiwan reiterated its stance of being a separate government to the People's Republic of China. It also accused China of bullying Taiwan in the international community, saying that China's bid to join the CPTPP is aimed at blocking Taiwan from entering international trade blocs.
In response, China's foreign ministry spokesperson said his country was firmly opposed to Taiwan's accession bid for the CPTPP.
"There is only one China in the world and Taiwan is an inalienable part of China's territory. With regard to the CPTPP, we firmly oppose Taiwan's accession to any agreement or organisation of official nature," China's Ministry of Foreign Affairs spokesperson Lijian Zhao said.
China also sent 19 aircraft into Taiwan's air defence zone following the news, Taiwan's Ministry of Foreign Affairs said.
For a government to join the CPTPP, all CPTPP members must unanimously approve the government's application.
Earlier in the week, Australia's Trade Minister Dan Tehan said China would need to reopen dialogue with Australia "on a minister-to-minister level" if Australia were to consider allowing China to join the trade pact.
"All parties will want to be confident that any new member will meet, implement, and adhere to the high standards of the agreement as well as to their WTO commitments and their existing trade agreements, because it's in everyone's interests that everyone plays by the rules," Tehan said.
The CPTPP applications follow Australia, alongside the UK and US, announcing a trilateral security pact aimed at addressing the defence and security concerns posed by China within the Indo-Pacific region.
Although China was not mentioned when announcing AUKUS, Australian Prime Minister Scott Morrison said the Indo-Pacific region was increasingly becoming "more complex". AUKUS will see the three countries create initiatives that increase cyber capabilities, artificial intelligence, quantum technologies, and undersea capabilities. The three countries will also promote deeper information and technology sharing between themselves.
Alongside China and Taiwan, the United Kingdom also submitted a formal request to join the CPTPP earlier this year, and a working group for its accession has been established.
Current members of the CPTPP include Australia, Brunei, Canada, Chile, Japan, Malaysia, Mexico, New Zealand, Peru, Singapore, and Vietnam.