The row between Asia's two biggest economies was triggered by a suggestion from new premier Takaichi that Tokyo could intervene militarily in any attack on the island, which China claims as part of its territory.

In a phone call with Trump on Monday, Chinese leader Xi Jinping pressed the ever-sensitive issue, saying its return was an "integral part of the post-war international order", according to China's foreign ministry.

Shortly after, "Trump set up a call with Takaichi and advised her not to provoke Beijing on the question of the island's sovereignty", the WSJ said, citing Japanese officials and an American briefed on the call.

"The advice from Trump was subtle, and he didn't pressure Takaichi to walk back her comments," the WSJ reported.

A spokeswoman for Takaichi's office declined to comment when contacted by AFP.

In her reporting of the call, the Japanese premier said she and Trump discussed his conversation with Xi, as well as relations between the two allies.

"President Trump said we are very close friends, and he offered that I should feel free to call him anytime," she said.

But according to the WSJ, "the Japanese officials said the message was worrying".

"The president didn't want friction over Taiwan to endanger a detente reached last month with Xi, which includes a promise to buy more agricultural products from American farmers hit hard by the trade war."

China has been furious in the wake of Takaichi's comments, summoning Tokyo's ambassador and advising its citizens against travel to Japan.

The release of at least two Japanese movies have also be postponed in China, according to Chinese state media.