Plans for an unprecedented meeting between the presidents of China and Taiwan sparked protests outside Taipei's parliament, the Legislative Yuan, on Wednesday.
Taiwan's President Ma Ying-jeou will meet his Chinese counterpart Xi Jinping in Singapore on Saturday, in the first high-level meeting across the Taiwan Straits since the end of the civil war in 1949.
Protesters said they are worried about the effect closer ties with China's ruling Communist Party, once Taiwan's sworn enemy, could have on the island's democratic way of life.
Ma will meet Xi, whose government regards Taiwan as a breakaway province awaiting reunification under Beijing's rule, just three months before he steps down as president at the end of a second term, and amid growing popular support for the pro-independence opposition Democratic Progressive Party (DPP).
"Beijing's move will affect the coming presidential election, as well as being a shot at Taiwan's democracy," Soochow University political analyst Hsu Yung-ming told reporters on Wednesday.
Meanwhile, DPP chairwoman and presidential candidate Tsai Ing-wen, said she was "very surprised" to hear about the presidential meeting.
"To turn the matter of cross-straits relations into a political maneuver will have a negative effect on the future of cross-straits relations in the long term," Tsai told reporters.
"Nor will it receive the recognition and acceptance of the people of Taiwan."
"I wish to remind President Ma in the gravest terms that cross-straits relations should be free of partisan politics, and particularly considerations of the interests of a particular party," she said.
"Taiwan's future shouldn't be used for electioneering."
Her party issued a statement hitting out at Ma's decision for being anti-democratic.
"President Ma has stated in the past that if a Ma-Xi meeting were to occur, it must be conducted under the conditions of 'national necessity, popular support, and legislative oversight,'" the DPP said in a statement.
"Ma's decision ... is unacceptable to the Taiwanese people."
It said the decision was in keeping with Ma's "long record of opaque decision-making," and ran "counter to democratic principles."
Ma and Xi will "exchange views on cross-straits issues," according to presidential spokesman Charles Chen, with a view to "securing cross-straits peace."
"No agreement will be signed, nor any joint statement released," Chen said in a statement.
Growing public backlash
Wu Fei, a senior researcher at the Charhar Institute diplomatic think-tank, said Beijing still doesn't understand why former Taiwan president Lee Teng-hui brought in democratic reforms in the 1990s, which culminated in the island's first fully democratic presidential elections in 2000.
"There were gains and losses from the Lee Teng-hui period, but no trust in [his DPP successor] Chen Shui-bian," Wu said. "If there is no meeting while Ma Ying-jeou is still in power, then things could go backwards under DPP rule."
"Mainland China needs to find somebody it can deal with [on the Taiwan side] ... and Ma Ying-jeou, whose point of view is quite dependable, would seem to be that person," he said.
Closer ties with Beijing under Ma's Kuomintang (KMT) nationalist party have sparked a growing public backlash in Taiwan, expressed in last year's student-led Sunflower movement which occupied government buildings in protest at a proposed bilateral trade deal.
According to retired Shandong University professor Sun Wenguang, closer ties between Taiwan and the mainland have previously come through private and non-government channels.
"Private individuals generally want to see cross-straits relations develop in a peaceful direction," Sun told RFA.
"There is also a strong desire among ordinary people to see a free and democratic Taiwan exert its influence on the mainland."
Taiwan has been governed separately from mainland China throughout the Japanese occupation (1895-1945), and since the KMT nationalist regime fled to the island after losing a civil war to Mao Zedong's communists on the mainland in 1949.
Many of the democratic island's 23 million residents identify as Taiwanese rather than Chinese, and there is broad political support for de facto self-rule, if not formal independence.
Beijing has threatened to use military force, should Taiwan seek independent statehood, however.
Reported by Yang Fan for RFA's Mandarin Service, and by Tung Kuang-cheng for the Cantonese Service. Translated and written in English by Luisetta Mudie.