Beijing (AFP) - China on Friday praised US president Donald Trump's snub of Taiwan, noting that observers had called his decision not to take a second call from the island's president a "slap in the face".

President Donald Trump rattled China in December after taking a congratulatory call from the self-ruling island's new Beijing-sceptic president Tsai Ing-wen © AFP/File STAFF Beijing (AFP) - China on Friday praised US president Donald Trump's snub of Taiwan, noting that observers had called his decision not to take a second call from the island's president a "slap in the face".

Trump rattled China in December after taking a congratulatory call from the self-ruling island's new Beijing-sceptic president Tsai Ing-wen after his election, smashing decades of diplomatic precedent.

But after Tsai suggested another call could take place in an interview with Reuters Thursday, Trump said he did not want to risk his newfound "personal relationship" with China's president Xi Jinping.

"I think he's doing an amazing job as a leader and I wouldn't want to do anything that comes in the way of that. So I would certainly want to speak to him first," Trump told Reuters in a separate interview.

China "has noted the US reaction," foreign ministry spokesman Geng Shuang told reporters during a regular press briefing, adding that online commenters "believe it's a slap in the face for Tsai Ing-wen".

"China always opposes that those with whom we’ve established diplomatic relations develop any formal or official exchanges with the Taiwanese side," he added.

Ties between Trump and Xi seem to have warmed recently after they met at Trump's Mar-a-Lago estate in Florida earlier this month.

Since then, Trump has praised China for helping pressure North Korea over its nuclear and missile programmes.

The two leaders have been "in constant touch" Geng told reporters.

Taiwan's presidential office stepped back from the idea of a call after Trump's comments.

FILE PHOTO: U.S. President Donald Trump welcomes Chinese President Xi Jinping at Mar-a-Lago state in Palm Beach, Florida, U.S. Thomson Reuters

"We understand the priority of the US side in handling regional issues and have no current planning (for another call) at this stage," it said in a statement Friday.

The comments were a "serious slap in the face" for Tsai, added political analyst Edward Chen of Tamkang University.

"Tsai is throwing the ball into Washington's court and Washington is saying no," he said.

However, lawmaker Chao Tien-lin of Tsai's Democratic Progressive Party said he thought Trump's response was reasonable.

"Washington needs Beijing in handling the North Korea issue," he said.

Concerns that Taiwan would become a bargaining chip were raised soon after Trump's election, when he suggested he may abandon the "One China" policy that underpins US-China relations, unless he could strike better deals with Beijing.

He later went on to say he would honour the policy, which acknowledges that there is only one China and Taiwan is part of it.

Taiwan is a self-ruling democracy but China sees it as part of its territory to be reunified, by force if necessary.

The US is the island's most powerful ally and arms supplier, despite having no official relations with Taipei after switching recognition to Beijing in 1979.

Relations between Taipei and Beijing have rapidly deteriorated since Tsai took the reins almost a year ago, ending an eight-year cross-strait rapprochement.

Beijing has cut all official communication with Taipei.