Though it's hardly surprising, given President Trump's stridently anti-China rhetoric during the campaign, relations between the US and China have deteriorated to a dramatic degree since the beginning of 2018. And with the US and China trading threats following the US's decision to sanction a branch of the Chinese military for buying arms from Russia (as China threatened the US with unspecified "consequences" if it didn't undo its "mistake"), the US has thrown gasoline on the fire by moving ahead with a planned sale of F-16 fighter jets and other weaponry to Taiwan in defiance of China's warnings, per Reuters and Bloomberg.

The arms sale follows China's participation in joint military drills with Russia earlier this month, as well as drills in the Strait of Taiwan earlier this year that were intended to simulate an invasion.

Taiwan welcomed the arms package, adding that a "case-by-case" approach to arms sales might be more efficient than previous large shipments of arms. According to Reuters, the order includes parts for both US-made and domestic fighter aircraft as well as tools to help Taiwan maintain its "defensive and aerial fleet" as mainland China has never renounced the "use of force" to bring Taiwan under control.

The $330 million request covers spare parts for "F-16, C-130, F-5, Indigenous Defense Fighter (IDF), all other aircraft systems and subsystems, and other related elements of logistics and program support," the Pentagon said, adding that it notified Congress of the possible sale. Lockheed Martin Corp (LMT.N) makes the F-16. The Pentagon said the proposed sale is required to maintain Taiwan’s "defensive and aerial fleet," and would not alter the military balance in the region.

In response, China "strongly" urged the US to honor "One China" principle and immediately revoke its sales of military hardware to Taiwan, Chinese defense ministry spokesman Ren Guoqiang said. Chinese Foreign Minister Geng Shuang echoed that warning in a Tuesday press briefing, saying that U.S. arms sales to Taiwan were a serious breech of international law and harmed Chinese sovereignty and security interests.

China strongly opposes the planned arms sales and has already lodged “stern representations” with the United States, he told a daily news briefing in Beijing.

China on Tuesday expressed dissatisfaction and said it had lodged stern representations with the United States after the State Department approved the sale to Taiwan of spare parts for military aircraft worth up to $330 million. China’s foreign ministry spokesman Geng Shuang made the comments at a daily news briefing in Beijing. U.S. military sales to self-ruled Taiwan, which China claims as its territory, are an irritant in ties between the world’s two largest economies. Taiwan would still need to finalize sale details with U.S. companies.

Notably, the arms sale follows China's decision to call off trade talks with the US set for this week, ratcheting up trade tensions between the two countries and rattling markets as investors started to doubt whether the trade conflict between the world's two largest economies would come to a swift and amicable solution.

The US has approved $1.3 billion in arms sales to Taiwan since Trump's victory in the 2016 election. Trump nearly triggered a diplomatic crisis later that year when he accepted a congratulatory phone call from the leader of Taiwan, which China interpreted as an insult and a violation of the "One China" policy that has held since the days of Richard Nixon.

Faced with a newly defiant Taiwan, Chinese President Xi Jinping has repeatedly warned that the mainland won't "give up an inch" of territory when it comes to its rogue province, while also warning that attempts to drive a wedge between Taiwan and China would be "punished by history."

Trump’s relationship with Taiwan has been a hot issue for China since he accepted a congratulatory phone call from President Tsai Ing-wen after his election and questioned why the U.S. recognizes Beijing instead of Taipei, a policy that underpins China-U.S. relations.