Wang added that during the talks Chinese and US officials had also agreed to step up cooperation to "tackle international terrorism and separatism".
"We also asked the United States to restrain and prevent activities by any person who takes advantage of the territory of the United States to conduct separatist activity."
Commenting on the riots, Wang said what had happened in Xinjiang was "a highly violent terrorist act involving beatings, smashings and arson."
"The response of the United States has been somewhat cold"
exiled Uighur leader
While avoiding names, Wang's comments follow earlier criticism from Beijing of Rebiya Kadeer, a Uighur activist who was jailed in China for several years and now lives in exile in the US.
China has labelled Kadeer, who leads the World Uighur Congress, a "terrorist" and says she instigated the Xinjiang unrest.
On Wednesday Kadeer herself expressed disappointment at the US response to the Xinjiang violence.
"The response of the United States has been somewhat cold," she said after arriving in Tokyo.
"I am perplexed and disappointed."
|China has asked the US to stop "separatist activities" by US-based Uighurs [AFP]
Shortly before Wang spoke in Washington, Hillary Clinton, the US secretary of state, told reporters that the US had voiced "concern" over the unrest with Chinese officials.
"We discussed a number of human rights issues, including the situation in Xinjiang, and we expressed our concerns. It was certainly a matter of great interest and focus," Clinton said without elaborating.
Xinjing's capital, Urumqi, has been tense since rioting erupted on July 5 after Chinese authorities stopped a protest by Uighur residents.
Demonstrators from the mainly Muslim Uighur community smashed windows, burned cars and beat Han Chinese, the dominant ethnic group in China.
Two days later, groups of Han residents took to the streets and attacked Uighurs.
Shortly after clashes began Clinton said the US was "calling on all sides to exercise restraint".
China has defended its policies on ethnic minorities, blaming the Xinjiang violence on separatists such as Kadeer.