China told the United States Sunday not to send the wrong signals to "Taiwan separatist forces," a day after urging Washington to cancel a planned missile sale to the island.

"The activities of Taiwan separatists pose a major threat to peace and stability in the Taiwan Strait," Xinhua news agency quoted Chinese State Councillor Tang Jiaxuan as telling US Deputy Secretary of State John Negroponte.

US Deputy Secretary of State John Negroponte (L) meets with Chinese Foreign Minister Li Zhaoxing in Beijing. [AFP]

"We hope the US side will implement its commitments, not send any mistaken signals to 'Taiwan independence' separatist forces and work together to maintain peace and stability in the Taiwan Strait and Sino-US relations."

Negroponte was in Beijing only days after the United States agreed to a plan to sell Taiwan 450 air and ground missiles.

"I stressed that any weapons sale that we might make to Taiwan would be for strictly defensive purposes and consistent with our one-China policy," Negroponte told reporters late Sunday.

"We had good frank discussions. We discussed bilateral and strategic issues including North Korea, regional security, the war on terrorism and trade," Negroponte said.

A working group on denuclearisation, agreed to in a breakthrough in six-nation talks on North Korea's nuclear programme last month, would begin work within days, he said.

The US envoy, who met earlier Sunday with Chinese Foreign Minister Li Zhaoxing, said he had discussed Iran, but gave no further details.

"The United States and China have wide common interests and many common concerns both bilaterally and in international affairs," Xinhua quoted Negroponte as saying.

"The United States side hopes to continue with China contacts and exchanges at all levels and in every area in order to strengthen our constructive relations."

Chinese Vice Foreign Minister Dai Bingguo told Negroponte on Saturday that China "resolutely opposes" US weapons sales to Taiwan, according to a Chinese foreign ministry spokesman.

Ties have recently cooled somewhat after US Vice President Dick Cheney's comments, on a trip to Australia, that China's military growth did not chime with its stated peaceful aims.

Negroponte's visit to Beijing is the second leg of a trip that has already taken him to Japan and will include a stop in South Korea.

All three are US partners in the six-nation effort to get North Korea to give up its nuclear weapons and part of his trip has focused on how to make sure Pyongyang holds up its end of the deal.

After exhaustive negotiations, a new six-nation agreement was signed last month under which Pyongyang agreed to give up its nuclear weapons programmes in exchange for economic and energy aid.

During talks between Li and Negroponte, China offered its condolences and sympathy after a series of tornadoes swept the southern United States, killing scores of people.