Without mentioning Pelosi by name, Qin said China opposes "any encouragement and support for the secessionist schemes of the Dalai clique."
On Friday, authorities intensified a manhunt for people accused of violence, posting photos taken from video cameras and security footage on Internet portals.
The 21 people are accused of endangering national security, and cited for beating, smashing, looting and arson.
One suspect was shown wielding a long sword and another was a mustached man who had been shown on news programs slashing another with a long blade.
Xinhua said two of the 21 suspects were arrested and a third turned himself in. Authorities offered rewards for information and promised anonymity to tipsters.
Police have arrested 24 people and another 183 turned themselves in, Xinhua said.
Outside of Lhasa, Beijing has deployed troops across a wide swath of western China, where more than half of China's 5.4 million Tibetans live.
Moving from town to town, police set up blockades and checkpoints to keep Tibetans in and journalists out.
The mobilization was helping authorities reassert control after demonstrations flared in Sichuan, Qinghai and Gansu provinces, inspired by monks in the Tibetan capital of Lhasa.
In Lhasa on Friday, residents said police patrolled the streets but people were free to go where they wanted as long as they had identity cards. In ethnic Tibetan areas of Sichuan and Gansu, residents said security forces set up armed encampments and hundreds of troops were patrolling towns.
State television, in its first footage of the confrontation between protesters and police last Sunday in the Tibetan town of Aba, showed dozens of crimson-robed monks charging at a line of police standing behind plastic riot shields.
Crowds of ordinary people threw rocks and one threw a Molotov cocktail as cars burned in the streets.
Also see: BEIJING 2008: Live Tiananmen Square broadcasts under threat
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