China has announced the first details of a controversial law that would allow it to use force against Taiwan.
Wang Zhaoguo gave few details of the proposed law
Legislator Wang Zhaoguo said such means would only be used as a last resort, if peaceful reunification efforts failed.
A BBC correspondent in Beijing says anyone seeking clarity on the law will be disappointed, since the explanations were both brief and vague.
China sees Taiwan as its territory, and has threatened to use force if the island formally declares independence.
Taiwanese lawmakers responded quickly and angrily to the proposed legislation, saying it was a pretext for attack.
"It has caused tension in the region," said Chiu Tai-shan, vice chairman of Taiwan's Mainland Affairs Council.
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
"Communist China tries to use this bill to deny the sovereignty of the Republic of China [Taiwan] and unilaterally change the status quo of the Taiwan Strait," he added.
The draft law - known as the "anti-secession law" - is designed to spell out the legal steps required before China would take action against Taiwan.
"If possibilities for a peaceful reunification should be completely exhausted, the state shall employ non-peaceful means and other necessary measures to protect China's sovereignty and territorial integrity," Wang Zhaoguo, a senior legislator, told delegates at the National People's Congress.
The proposed law does not give details of what developments might trigger Chinese action.
Some analysts said China's emphasis on "non-peaceful" means appeared designed to include alternatives to military force, such as blockades or sanctions.
Mr Wang insisted that Beijing was still committed to a peaceful resolution.
"So long as there is a glimmer of hope for peaceful reunification, we will exert our utmost to make it happen rather than give it up," he told China's parliament.
But he added: "No sovereign state can tolerate secession, and every sovereign state has the right to use necessary means to defend its sovereignty and territorial integrity."
Mr Wang also argued that China's basic policy towards Taiwan remained the "one country, two systems" formula, as is already employed in Hong Kong.
A final vote on the bill has been scheduled for Monday 14 March. According to a BBC correspondent in Beijing, Louisa Lim, there is no doubt that the bill will be passed, because the Chinese parliament is largely viewed as a rubber stamp.
'Blank cheque to invade'
Taiwan issued a strong protest against the draft law on Tuesday, saying it could set the stage for an attack by China.
The Mainland Affairs Council, which handles the island's policy on China, said the law "gives the [Chinese] military a blank cheque to invade Taiwan" and "exposed the Chinese communists' attempt to use force to annex Taiwan and to be a regional power."
"Our government lodges strong protest against the vicious attempt and brutal means... to block Taiwanese from making their free choice," the council said in a statement.
China says the law was prompted in part by proposals to change Taiwan's constitution. Beijing is concerned that a declaration of formal independence might be included in the constitution's new wording.
President Chen has repeatedly denied this, saying the changes are needed to modernise the way the island is governed.
He has also pledged not to move Taiwan towards independence during his term of office.