"They are not our friends, they need us for their own ends," President Baron Waqa told reporters.
"I'm sorry, but I have to be strong in this because nobody should come and dictate things to us."
The annual Pacific summit this year, which ends in Nauru on Thursday, has been one of the most controversial in the 49-year history of the event.
The usual discussions on climate change have been overshadowed by the dispute between the host and China and their treatment of asylum seekers on the island under an agreement with Australia.
The diplomatic dispute confronts Nauru, with a population of 11,000 inhabitants and an area of only 21 square kilometers (8 square miles), against the Asian superpower.
It erupted on Tuesday when the head of the Chinese delegation, Du Qiwen, tried to address a meeting, but Waqa refused to let him speak until the leaders of the island were finished.
The Chinese delegation then came out furious, with Du, reportedly walking striding across the room to emphasize their disgust before leaving.
"Would you behave like this in front of your own president? I doubt it," Waqa told a news conference Wednesday night.
"He disrespected the Pacific, the islands leaders of the forum and other ministers who have joined us in our territory." You're kidding? Look at him, he's nobody.
"He is not even a minister and demands to be recognized and speak before the prime minister of Tuvalu.
& # 39; Bad farce & # 39;
Waqa, whose country backs Taiwan on its arch rival China in the battle for diplomatic recognition, had already infuriated Beijing before the summit began in a row for visas.
The exchange with Du highlighted the sensitivities on Beijing's growing influence in the Pacific, where China provided an estimated US $ 1.78 billion in aid to island nations between 2006-16.
"We see that many large countries enter and, sometimes, make their way across the Pacific, some are extremely aggressive, even to the point of trampling on us," Waqa said.
"From this forum, all the leaders (now) know how arrogant some of these people are."
He said such behavior deserved an apology from Beijing.
"We will not seek an apology, we will even take it to the UN," he said. "Not only that, I will mention it at the UN and at every international meeting."
China has shown no signs of retreating, and a spokeswoman for the Foreign Ministry said on Wednesday that Nauru violated the forum's regulations "and organized a bad farce."
China does not belong to the PIF, but it is one of 18 countries that attends the summit of leaders as a "dialogue partner" for discussions with member countries.
Beijing and Taipei have competed for diplomatic influence in the Pacific for decades, with both sides offering help and support to small island states in exchange for recognition.
Taiwan paid much of the infrastructure used in the Nauru PIF and there could be similar tensions at next year's event in Tuvalu, which also recognizes Taipei.
China sees Taiwan as part of its territory awaiting reunification, by force if necessary, even though the island considers itself as a sovereign nation and is a self-governing democracy.
Meanwhile, Australia and New Zealand have boosted their foreign aid programs in the Pacific to counter Chinese influence in a region they consider their backyard.