The US State Department said on Saturday that the sale contributed to “security and stability” between Taiwan and China, Reuters reported. Beijing announced a series of moves against the US in retaliation for the proposed $6.4bn (£4bn) sale. Ties between the two countries are already strained by rows over trade and internet censorship. The US is the leading arms supplier to Taiwan and has a treaty obligation to provide it with defensive arms. Beijing said it would suspend military exchanges with the US, review co-operation on major issues and impose sanctions on companies selling arms. However, the US – like the EU – has banned its companies selling arms to China since the 1989 Tiananmen Square massacre, so it was not clear what effect Chinese sanctions would have. Taiwan and China have been ruled by separate governments since the end of a civil war in 1949. Beijing has hundreds of missiles pointed at the island and has threatened to use force to bring it under its control if Taiwan moved towards formal independence. US lawmakers have 30 days to comment on the proposed sale, Associated Press reported. If there are no objections, it would proceed. The arms package includes 114 Patriot missiles, 60 Black Hawk helicopters and communications equipment for Taiwan’s F-16 fleet, the agency said in a statement.