Citing the "very complex and sensitive" situation in cross Straits relations, China has asked the US to cancel its plans to sell sophisticated weapons to Taiwan, further emboldening the pro-independence forces on the self-ruled island.

"China firmly opposes the US arms sales to Taiwan," Foreign Ministry spokesperson Jiang Yu said and urged the US to immediately cancel the deal.

The US would seriously violate its commitments to China made in the three Sino-US joint communiques, in particular the joint communique signed between the two nations in 1982, if it sells P-3C antisubmarine aircraft and other advanced weapons to Taiwan, she said.

She said the arms sales to Taiwan also constitutes wanton interference in China's internal affairs, noting the Chinese side has expressed strong objection and lodged a protest with the US.

Washington switched diplomatic recognition from Taipei to Beijing [Images] in 1979.

However, the US continues to be the main ally and main defence supplier of the cash-rich island, which Beijing views as a rebel province that must be reunified with the mainland, even by force.

"China reserve the rights of further action," Jiang said.

The US Department of Defence on Wednesday announced tentative plans to sell 12 P-3C antisubmarine aircraft and 144 cruise missiles to Taiwan.

The current situation across the Taiwan Straits is "very complex and sensitive," Jiang said, referring to Taiwan government's push for a referendum on UN membership in the name of Taiwan.

Jiang urged the US to adhere to its solemn commitments on the Taiwan issue with concrete actions, immediately cancel the tentative plans of arms sales to Taiwan, stop selling weapons to Taiwan, end its military links with Taiwan and stop sending any wrong signals to "Taiwan independence" secessionist forces.

China on Sunday had accused Taiwan President Chen Shui-bian of seeking personal interest with his latest "Taiwan independence" remarks, warning that Beijing is ready to face "serious situations" across the Taiwan Straits.

Addressing a rally on Saturday, Chen feverishly whipped up support for his "referendum" plan on Taiwan's entry into the United Nations and described the self-ruled island being a "sovereign state."

"We will keep a close watch over developments on the other side of the Strait and have got prepared to cope with serious situations," Xinhua news agency quoted a spokesman for the Taiwan Affairs Office of the Chinese Cabinet.

The spokesman said the mainland has been endeavouring to improve cross-Strait relations with the utmost effort, but will never allow any people to separate Taiwan from the motherland in any manner.

China and Taiwan split in 1949 at the end of a civil war, but Beijing still claims the self-ruled island as part its territory.

China has repeatedly threatened to invade if Taiwan declares independence or drags its feet on reunification talks.

Moreover, the Chinese parliament has also passed an anti-cession Law in 2005 to foil Taiwan's bid to seek independence.

Over the last 14 years, Taiwan had annually applied for UN membership as 'Republic of China', but this year marks the first time for it do so as 'Taiwan'.