"The US plan will definitely undermine China-US relations and bring about serious negative impact on exchange and co-operation in major areas between the two countries."
'Gravity of issue'
Baodong said China "strongly urges the US side to fully recognise the gravity of the issue, revoke the erroneous decision on arms sales to Taiwan and stop selling any weapons to Taiwan".
Laura Tischler, a US state department spokesman, said: "This is a clear demonstration of the commitment that this administration has to provide Taiwan the defensive weapons it needs and as provided for in the Taiwan Relations Act."
She said that the arms deal would contribute to "maintaining security and stability across the Taiwan Strait".
Taiwan welcomed the US decision, with Ma Ying-jeou, the country's president, saying the deal would help the island further develop ties with China.
|Al Jazeera speaks to Yue Xiaoyong, China's ambassador to Qatar, about the US decision
"It will let Taiwan feel more confident and secure so we can have more interactions with China," he was quoted by Taiwan's Central News Agency as saying.
The developments incidentally come against a backdrop of steadily improving relations between the two countries.
Speaking to Al Jazeera on Saturday, Christian Ford, Beijing bureau chief for the US newspaper Christian Science Monitor, said that while tensions between China and the US have been rising, those between China and Taiwan have been abating in recent months.
"The two sides have been discussing trade and investment issues ... there are now many more flights from Beijing to Taiwan," he said.
"The actual situation in the streets is not tense. In fact, it's a great deal less tense than a couple of years ago.
"But when you look at relations between and Washington and Beijing, there are definitely some more hiccups on the horizon."
Ford mentioned an expected meeting between Barack Obama, the US president, the Dalai Lama, the Tibetan spiritual leader, as a case in point.
"When that happens, Beijing is bound to react," he said.
Beijing regards Taiwan as a renegade province and has vowed to bring the island eventually back under mainland rule, by force if necessary.
The US government, on the other hand, is bound by the 1979 Taiwan Relations Act, which obliges Washington to ensure the island is capable of responding to Chinese threats, and to sell defensive weapons to it.
|The US announced it was selling $6.4bn worth of military hardware to Taiwan [Reuters]
Wang, the Chinese embassy spokesman, said that the weapons deal violated the 1982 communique between China and the US, which said the arms sales to Taiwan "will not exceed, in qualitative or in quantitative terms," the level in the years before that.
The Obama administration told the US congress on Friday of the proposed sales, which include Black Hawk helicopters, Patriot "Advanced Capability-3" anti-missile missiles and two refurbished Osprey-class mine-hunting ships.
Philip Crowley, a state department spokesman, said that the arms sales were consistent with the three key communiques between the United States and China when they normalised relations.
However, Yue Xiaoyong, China's ambassador to Qatar, told Al Jazeera that the arms sales were "a clear violation of the three joint communiques".
"It's a clear violation of China's sovereignty and territorial integrity," he said.
In 2008, China suspended most military dialogue with Washington after the administration of George Bush, the former president, approved a $6.5bn arms package to Taiwan that included guided missiles and attack helicopters.