Donald Trump. Drew Angerer/Getty Images Prominent geopolitical expert Ian Bremmer slammed President-elect Donald Trump's decision to speak with the president of Taiwan by phone on Friday.

The call could strain US relations with China. Trump's call to President Tsai Ing-wen is the first time a US president has directly spoken with Taiwan's leadership in more than 30 years.

The US suspended formal diplomatic relations with Taiwan in 1979 after establishing a One China position in an effort to establish diplomatic channels with Beijing.

"Beijing will be absolutely incensed," Bremmer tweeted.

He continued:

Bremmer expanded on his thoughts in an email to Business Insider.

"Trump is just taking all sorts of calls of congratulations and has ignored both protocol and intel briefings," he said. "This is his first serious misstep accordingly. We'll surely see more."

He continued: "Inconceivable the Chinese won't react harshly to this. This is a red line for them. And hard to imagine Trump saying 'no big deal' and not talking to the Taiwanese going forward. We are now stuck [with] escalation, and US-China relations under Trump get off to a particularly ugly start."