The US has reacted with dismay to an anti-secession law that would allow China to use force against Taiwan.
Wang Zhaoguo gave few details of the proposed law
The White House described the planned law as "unhelpful", while a military chief warned about what he termed China's "significant" military growth.
US legislation obliges it to resist any use of force by China against Taiwan, and provide a means of defence.
China sees Taiwan as its territory, and has threatened to use force if the island formally declares independence.
Chinese legislators said that force would only be used as a last resort, if peaceful reunification efforts failed.
In separate statements, White House spokesman Scott McClellan and state department official Richard Boucher criticised the law.
Both branded the proposed legislation "unhelpful".
"We oppose any attempts to determine the future of Taiwan by anything other than peaceful means," Mr McClellan told reporters.
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
Mr Boucher said the state department had made it clear to Chinese and Taiwanese officials that passing legislation "is not going to help solve the problem".
Secretary of State Condoleezza Rice is reported to be planning a visit to China later this month.
Earlier, 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.
"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.
The proposed law does not give details of what developments might trigger Chinese action.
Delegates to the National People's Congress were told on Tuesday that China "shall employ non-peaceful means and other necessary measures" if hopes for peaceful reunification were "completely exhausted". Some analysts said China's emphasis on "non-peaceful" means appeared designed to include alternatives to military force, such as blockades or sanctions.
Announcing the bill, senior legislator Wang Zhaoguo argued that China's basic policy towards Taiwan remained the "one country, two systems" formula, as employed in Hong Kong.
Also on Tuesday Admiral William Fallon, head of the US Pacific Command, told the Senate Armed Services Committee in Washington that ongoing Chinese military procurement was a "cause for concern".
China has concentrated on building up its maritime capabilities, acquiring submarines and aircraft from Russia, as well as building its own.
"It seems to be more than might be required for their defence," Reuters news agency reported Adm Fallon as saying.