BEIJING — China expressed "serious concern" Monday after President-elect Donald Trump suggested he might tear up the basis for decades of bilateral relations between Washington and Beijing.

Trump said Sunday that he could do away with the so-called "one-China" policy — an agreement by the United States to effectively side with China in its sovereignty dispute with the self-proclaimed republic of Taiwan.

"China needs to prepare enough ammunition for a roller-coaster ride of the China-U.S. relations with Trump"

This brought a stinging rebuke from Beijing.

"China expresses serious concern on this subject," Chinese Foreign Ministry spokesman Geng Shuang told reporters. "If the [one-China policy] is compromised or interfered with, any sound and steady development in China-U.S. relations and cooperation in various fields is out of the question."

The Global Times, a Chinese state-run newspaper, went further, accusing Trump of being "very childish and impulsive."

Related: Trump Faults China, But Calls for 'Mutual Respect'

It said Trump's comments wouldn't be without consequences.

"China needs to prepare enough ammunition for a roller-coaster ride of the China-U.S. relations with Trump," it said in editorial. "There are many other people in the world that also need to buckle up the seat belts."

The newspaper said that "China needs to start a resolute battle with" Trump, adding that "China and other powers in the world are not going to be bullied."

Although the U.S. does not recognize Taiwan an independent nation, it maintains a strong non-official relationship with the island, which is around 80 miles from the Chinese mainland and is a little larger than the state of Maryland. This includes around $12 billion in arms sales since 2010.

Trump has repeatedly accused China of various foreign policy failings and what he deems unfair trade practices.

"We can't continue to allow China to rape our country," Trump told a rally in Indiana in May. "That's what they're doing. It's the greatest theft in the history of the world."

He further ruffled Beijing's feathers by speaking on the phone with the president of Taiwan, a self-proclaimed republic that China sees as an illegitimate breakaway state.

The President of Taiwan CALLED ME today to wish me congratulations on winning the Presidency. Thank you! — Donald J. Trump (@realDonaldTrump) December 3, 2016

Under the one-China policy, Washington has effectively agreed to take China's side in this dispute, and Trump's call broke with decades of diplomatic protocol between the two nations.

In his latest comments Sunday, Trump appeared to go one step further by suggesting in an interview with "Fox News Sunday" that he could end this policy altogether.

Related: China Flew Nuclear-Capable Bombers Near Taiwan Before Trump Call

"I fully understand the one-China policy, but I don't know why we have to be bound by a one-China policy unless we make a deal with China having to do with other things, including trade," Trump told Fox.

Trump’s threats to China during the presidential campaign verged on the declaration of a trade war, something many analysts have said would be a risky move.

Leading Chinese tech entrepreneurs also plan to capitalize on Trump’s hardline stance on immigration, which they see as an opportunity to lure talent away from the U.S.