A recently disclosed US memo on arms sales to Taiwan "is totally wrong and invalid", the State Council's Taiwan Affairs Office said on Thursday.

On Aug 30, the United States declassified a 1982 memo that US president Ronald Reagan sent to his secretary of state, George P. Shultz, and secretary of defense, Caspar Weinberger, after Beijing and Washington reached agreement on the Aug 17 Communiqué on US arms sales to Taiwan that year.

The document said Taiwan's defensive capability relative to that of the Chinese mainland would be maintained in both quantitative and qualitative terms.

Taiwan Affairs Office spokesman Ma Xiaoguang said the memo's contents were in severe violation of the one-China principle, the provisions of three Sino-US Joint Communiqués and the basic norms governing international relations.

"It is totally wrong and invalid," he said.

Peaceful development of cross-Straits relations is the key to peace and stability across the Taiwan Straits, he said. US arms sales to Taiwan would only "fuel" the arrogance of the "Taiwan independence" separatist forces and further undermine peace and stability across the straits.

Ma stressed that the peaceful development of cross-Straits relations is the common aspiration of compatriots on both sides.

"We are ready to do our utmost and strive with utmost sincerity for the prospect of peaceful reunification of the country," he said. "At the same time, we are unshakable in our determination to safeguard China's sovereignty and territorial integrity.

"China must and will be unified. This historical trend is unstoppable by anyone and any force."