China is lashing out at pro-independence politicians in Taiwan.
Remarks by Chinese Foreign Ministry spokesman Liu Jianchao were the strongest heard since Taiwan's parliament passed a new law last week, allowing the president to call a referendum on independence.
Mr. Liu said the talk of independence by some Taiwanese politicians is dangerous and says China considers it the biggest threat to peace and stability in the region.
Under the new law, Taiwan's president can order a referendum on sovereignty if the island is threatened by China. In most other cases, however, parliament can block referendums.
The island has been outside of Beijing's control since the end of a civil war in 1949, when Chinese Nationalists fled there to escape the Communist takeover of the mainland. But China considers Taiwan part of its territory.
China has always threatened to invade the island if it declares independence. Beijing recently strengthened its warnings, saying moves by Taiwan's leadership - such as the referendum on independence or the adoption of a new constitution - could trigger a war.
China's strong statements Tuesday were directed at Taiwanese President Chen Shui-bian, who last week began pushing to hold a sovereignty referendum on March 20, the day Taiwanese voters go to the polls in national elections.
Some have dismissed Mr. Chen's actions and the Chinese response as bluster, but the exchange is causing concern in Washington. The United States on Monday asked Taiwan not to change the status of the island.
China acknowledged the statement, and urged the United States - Taiwan's largest weapons supplier - to work to preserve stability in the Taiwan Straits.
Chinese officials say Taiwan will be high on the agenda when Chinese Prime Minister Wen Jiabao visits Washington later this month.