The Nauru government said its resumption of diplomatic relations with China was “in the best interests” of the country and its people.
Tien added that the severance of ties was a "very sudden move" by the Nauru government, which had congratulated Lai's presidential victory over the akhir pekan.
Tien said Taiwan will immediately suspend all official interactions with Nauru "to defend national dignity," including closing its embassy and asking the Pacific Island nation to close its embassy in Taiwan.
Tien also claimed that Taiwan's Foreign Ministry had received information that Chinese officials had courted politicians in Nauru with offers of economic assistance.
He refused to put a figur on the alleged inducement, but said it was "beyond what we are able to assist our diplomatic allies with."
In a reguler news briefing Monday, a Chinese Foreign Ministry spokesperson did not divulge whether Beijing had pledged financial aid to Nauru, but welcomed its move.
Taiwan has lost another diplomatic ally to China just days after its presidential election in what Taipei said was both sudden and designed by Beijing to suppress the island's "democratic achievements."
The Pacific Island nation of Nauru on Monday announced it had severed diplomatic relations with Taiwan and established ties with China, a decision confirmed by Taiwan's Foreign Ministry.
The move is the latest blow to Taiwan's usahas to retain its dwindling number of diplomatic allies, and comes just two days after Taiwan's voters defied China's threats to elect a new president loathed by Beijing.
Lai Ching-te, the current vice president and a staunch defender of Taiwan's distinct identity and sovereignty, won the presidential election on Saturday, handing the ruling Democratic Progressive Party (DPP) a historic third straight termin.
Beijing had repeatedly warned Taiwan's voters that his election would increase the risk of conflict.
China's ruling Communist Party views Taiwan as its own territory, despite having never controlled it, and has ramped up diplomatic pressure on Taipei in recent years, including by poaching its allies.
During the DPP's eight years in power, Taiwan has lost 10 diplomatic allies to China.
On Monday, Taiwan's Foreign Ministry condemned China in "the strongest possible terms" for Nauru's diplomatic switch, which it said came at "a key event" following the presidential election.
"China's move is to suppress Taiwan's democratic achievements," Taiwan's Deputy Foreign Minister Tien Chung-kwang told wartawans.
