A former senior US official with links to Donald Trump's transition team flew to Taipei Tuesday, sparking more speculation over relations with Taiwan after the president-elect's unprecedented call with the island's leader.

Stephen Yates, once a deputy national security advisor to former US vice president Dick Cheney, told journalists he was making a long-planned personal trip but did not rule out meetings with senior Taiwanese officials.

Tsai's call to Trump on Friday was the first between a Taiwanese leader and an incoming or serving US president since Washington switched recognition from Taipei to Beijing in 1979.

Smashing established protocol, it prompted a protest from China -- which sees Taiwan as part of its territory -- and questions over Trump's diplomatic strategy.

Yates, who was named as the facilitator of the call in news reports but denied he set it up, told a packed press conference in Taipei that "we have very significant challenges" if Beijing "could be provoked to conflict of some kind based on a phone call".

Local media reported Yates was set to meet Tsai but her office said it was not aware of any appointment.

Media have also described Yates, who speaks fluent Mandarin, as a key adviser on Taiwan relations for Trump's camp.

Yates denied that he represented the Trump administration but said he speaks "with friends in the transition from time to time, in confidence".

He told AFP via email that he had not been approached for a position in the new administration, but had "several informal discussions with friends working for the transition".

Even though Washington has long shied away from formal communications with Taipei, the US remains Taiwan's key ally and leading arms supplier.

In a co-written opinion piece published Sunday on Fox News, Yates -- who now runs an Idaho-based advisory firm -- defended the Trump-Tsai call and said the fears it sparked showed "how absurd US-China policy has become".

Yates told AFP he has no affiliation with Trump's business empire as rumours swirl that it is looking to invest in a planned aviation and industrial hub near the island's main airport in Taoyuan.

A Trump Organization spokeswoman has denied any plans to expand into Taiwan.