China on Saturday lodged a complaint with the United States against President-elect Donald Trump’s phone conversation with Taiwanese President Tsai Ing-wen on Friday, reported BBC. After the call, Trump’s transition team said the two leaders discussed “close economic, political and security ties”. Tsai, who happens to be Taiwan’s first female president, reportedly congratulated the New York businessman on his victory.

A day after the controversial conversation, Beijing urged Washington “to cautiously, properly handle Taiwan issue to avoid unnecessary disturbance to Sino-US relations”, reported China’s state news agency Xinhua.

Friday’s telephonic conversation between the leaders was a stark contrast to the US policy set in 1979 cutting all formal ties with the country. This was the first time since 1979 that the leader of the island and the US president or president-elect has communicated with each other.

Taiwan and US have long severed ties after the rapprochement between Beijing and Washington. The US embassy in Taiwan was also closed down in the 1970s. Taiwan is a democratically-ruled island that Beijing believes to be a breakaway province. But since the rapprochement, Washington has followed a ‘one China’ principle. According to it, Taiwan is considered to be part of the Chinese nation.

The White House, however, said that Trump’s conversation does not signal any change in US policy. “Our fundamental interest is in peaceful and stable cross-strait relations,” White House National Security Council spokesperson Ned Price told BBC.