Taiwan's president has condemned a new Chinese law giving it the right to use force against the island if it moves towards declaring formal independence.
Both sides have built up their military capability
In his first comments since the bill was passed on Monday, Chen Shui-bian described it as a "law of aggression".
President Chen said the people of Taiwan alone had the right to determine their country's future.
China sees Taiwan as its territory and says it reserves the right to use force if "peaceful reunification" fails.
The so-called anti-secession law allows for the use of "non-peaceful and other necessary measures".
Ruled by separate governments since end of Chinese civil war in 1949
China considers the island part of its territory
China has offered a "one country, two systems" solution, like Hong Kong
Most people in Taiwan support status quo
Analysts say the new law is partly designed to limit the options of President Chen, whose Democratic Progressive Party is pro-independence.
But it will add to tensions across the Taiwan Strait, where China has been rapidly building up its military capability.
Mr Chen said the law had heightened "regional tensions" and triggered "disturbances in the world community".
The two sides could only resolve their differences by dialogue, he said.
The president also repeated calls for a million people to join a mass street protest later this month.
The White House and Tokyo have also expressed concern following Monday's bill.
The US is Taiwan's closest ally and is worried about being sucked into any conflict between the island and China.
But China's Premier, Wen Jiabao, said the law was aimed at improving relations with Taiwan.
"This is a law to strengthen and promote cross-Strait relations, for peaceful reunification, not targeted at the people of Taiwan, nor is it a law of war," he said.
The new law was passed in the final session of the Chinese parliament's annual National People's Congress by a margin of 2,896 to zero, with two abstentions.