New York: President-elect Donald Trump broke with decades of US diplomatic policy Friday and spoke with President Tsai Ing-wen of Taiwan, at the risk of provoking a serious rift with China.

"During the discussion, they noted the close economic, political, and security ties" between Taiwan and the United States, Trump´s office announced in a read-out of the call.

"President-elect Trump also congratulated President Tsai on becoming President of Taiwan earlier this year," it said.

It was not immediately clear which side initiated the telephone call, one of several Trump has been making with world leaders since his election victory, or if it signals a policy shift.

China regards self-ruling Taiwan as part of its own territory awaiting reunification under Beijing´s rule, and any US move that would imply support for independence would cause grave offense.

Washington cut formal diplomatic relations with the island in 1979 and recognizes Beijing as the sole government of "One China" -- while keeping friendly non-official ties with Taipei.

But Tsai has refused to accept the concept of "One China," prompting Beijing to cut off all official communication with the island´s new government.

Tsai´s Democratic Progressive Party government (DPP) came to power after a landslide victory in January over the Kuomintang (KMT), which had much friendlier ties with Beijing.

Trump, based at his New York offices while he prepares to move to the White House next month after his inauguration, has taken congratulatory calls from dozens of world leaders.

But, until Thursday, State Department officials had been telling reporters that he had not asked for official briefing on current policy from US diplomats before making the contacts.

On Friday, department spokesman John Kirby said the outgoing US administration has now helped with "some foreign communications that the transition team has gone forward with."

But he referred reporters to Trump´s office for details and would not say whether the president-elect himself had requested any background briefings before making or taking any calls.

Asked whether Trump was among those on the transition team who received such help, a senior US official would only say that Vice President-elect Mike Pence has also made foreign calls.