Thousands of people have joined an opposition rally in Taiwan, protesting against President Chen Shui-bian's pro-independence stance.
KMT leader Ma is blocking a multibillion-dollar arms deal
In the second demonstration in a week, they urged Mr Chen to stop stoking tensions with China, by scaling down a controversial weapons deal with the US.
Opposition parties say the president should instead focus on the economy.
Mr Chen addressed supporters at a rally on Saturday, highlighting the perceived military threat from China.
"We oppose ultimate unification as the sole option for Taiwan's people as it runs against the principle of democracy," Mr Chen told the rally.
"Our future will only be decided by the 23 million people of Taiwan."
Last year China passed a law to allow the use of force if Taiwan formally declares independence. China has more than 700 missiles targeted at Taiwan.
Opposition Nationalist Party (KMT) chairman Ma Ying-jeou addressed the rally, saying relations with China were not what mattered most to the people of Taiwan.
"People care most about the economy, about whether the many corruption scandals are thoroughly probed," Mr Ma said.
He is now flying to Washington to explain why his party is blocking a multibillion dollar arms deal between the two countries.
The opposition alliance of the KMT and the People First Party (PFP) have said they want the $16bn (£9bn) deal proposed by Mr Chen's administration scaled down.
"Taiwan can't possibly win a war with China. The weapons deal is impractical and too expensive, especially after six years of poor economic performance under Chen's bad governance," PFP lawmaker Daniel Huang said.
Unlike Mr Chen's Democratic Progressive Party, the KMT and PFP favour improved ties with Beijing.
Mr Chen reignited tensions last month when he closed an advisory council on reunification with China - a move described by China as a "dangerous step".
Mr Chen defended the move saying he was prompted by Beijing's persistent military threat and attempts to use non-peaceful means to unilaterally change the "status quo" in the Taiwan Strai