China lashed out at a declaration by Pacific Island leaders that upheld decades of engagement with Taiwan on Friday, branding it a "mistake" that "must be corrected".
After five days of talks in Tonga, the 18 members of the Pacific Islands Forum rebuffed Chinese efforts to stop Taiwan from attending future summits as a "development partner".
In a final communique, the bloc's leaders "reaffirmed" a 1992 agreement that allowed Taipei to take part.
China's special envoy to the Pacific Islands, Qian Bo, reacted to the statement with disbelief.
"It must be a mistake. It must be a mistake. You know, this is certainly not the consensus," he told journalists at the summit.
"This is a surprising mistake made by someone, I'm not sure, but I think it must be corrected."
Qian said he had contacted the bloc's secretariat in the hope of clarifying the situation.
"This should not be the final communique, there must be a correction on the text."
China also attends Pacific Island summits as a development partner.
Beijing has aggressively sought to exclude Taiwan -- a self-governing island of more than 23 million people -- from international fora and rejects its claims to autonomy.
Solomon Islands, China's main partner in the South Pacific, had lobbied for Taiwan to be stripped of its partner status with the Pacific Islands Forum.
But the move angered some of Taiwan's allies.
The Pacific Islands Forum is split between countries that have diplomatic relations with Beijing, and others like the Marshall Islands, Palau and Tuvalu that are allies of Taipei.
Qian said the balance was heavily in Beijing's favour, something that was not reflected in the summit statement.
"The situation is obvious: among the 18 members of the (Pacific Islands Forum), 15 countries have diplomatic relations with China," he said.
Taiwan sent deputy foreign minister Tien Chung-kwang to Tonga, seeking to reinforce ties with its shrinking list of Pacific Island allies.
China's Ministry of Foreign Affairs said Friday that "the Taiwanese authorities' attempt to gain visibility by participating in international meetings only serves to deceive themselves and bring humiliation upon themselves".