The Taiwanese foreign ministry on Saturday accused China of an "arbitrary intervention" after a joint declaration by Pacific leaders was altered to remove mentions of Taiwan.
"Taiwan issued the strongest condemnation on China's arbitrary intervention and unreasonable actions that undermine regional peace and stability," the foreign ministry told AFP in a statement.
Self-ruled Taiwan -- which Beijing claims as its own territory -- also called on "all like-minded countries to closely monitor China's actions" to safeguard "the harmony and stable development of Pacific island countries".
The rebuff came after a statement by Pacific leaders was reissued with mentions of Taiwan removed after China had slammed an earlier version as a "mistake" that "must be corrected".
After five days of talks in Tonga, a "cleared" communique was released Friday that reaffirmed a 30-year-old agreement allowing Taiwan to take part in the Pacific Islands Forum (PIF).
But the wording immediately raised the ire of Chinese diplomats, who piled pressure on Pacific leaders to amend the document.
The forum reissued the communique without explanation Saturday morning, conspicuously deleting the paragraph concerning the regional bloc's "relations with Taiwan".
Neither PIF nor Chinese officials replied to requests for comment on Saturday.
China's special envoy to the Pacific islands, Qian Bo, had told reporters on Friday that the mention of Taiwan was "a surprising mistake made by someone", before insisting "it must be corrected".
Qian earlier said he had contacted the bloc's secretariat in the hope of clarifying the situation.
The original paragraph -- titled "Relations with Taiwan/Republic of China" -- said leaders had "reaffirmed" the 1992 decision that paved the way for Taiwan's participation in the forum.
Beijing has aggressively sought to exclude Taiwan, a self-governing island of more than 23 million people, from international bodies and rejects its autonomy.
The South Pacific was once seen as a bastion of support for Taiwan's claim to statehood, but China has methodically whittled this down.
In the past five years, Solomon Islands, Kiribati and Nauru have all been persuaded to switch diplomatic recognition from Taipei to Beijing.
Beijing insists its diplomatic allies withdraw recognition of the self-ruled island.
Palau, Marshall Islands and Tuvalu maintain diplomatic relations with Taipei but face constant pressure to change.
Taiwan's foreign ministry said it had contacted its three Pacific allies "to actively communicate with the PIF Secretariat" in a bid to retain the clause.
"But the final decision by member states was to use the spirit of diversity and inclusion of the 'Pacific Way' as a compromise of the opinions of all parties, and publish a joint communique with consensus," a Taiwanese spokesperson added.
"This communique did not undermine our country's status in the Pacific Islands Forum or exclude our rights to participate in the PIF in the future.
"The Ministry of Foreign Affairs thanked our allies and like-minded countries for their support for our continued participation in PIF."
Solomon Islands, China's main partner in the South Pacific, has lobbied for Taiwan to be stripped of its "development partner" status with the PIF.
US territories Guam and American Samoa were elevated to associate members of the forum, against the wishes of Solomon Islands.
New Zealand's foreign ministry confirmed to AFP that there had not been a consensus on the paragraph about Taiwan.
"There are a range of views among the 18 Pacific Islands Forum members and part of the 'Pacific Way' is respect for different views and the importance of consensus," a spokesperson said in a statement.
