Donald Trump hasn’t officially been sworn in as president yet and already broke a longstanding diplomatic tradition when he took a phone call from the president of Taiwan.

The U.S. broke off ties with Taiwan in 1979 and Washington has since followed a so-called “one China” policy.

The President’s office in Taiwan said its president and Trump talked about strengthening bilateral interactions and discussed the possibility of a closer cooperation between the two sides.

Reports say as statement from the president-elect’s transition team said the Taiwanese president offered her congratulations to Trump.

The move initially drew an irritated response from China, but reports suggest comments from Chinese Foreign Minister Wang Yi downplayed the significance of the call.

The minister says the call to Trump was “just a small trick by Taiwan.”