Washington (AFP) - President Donald Trump has often bragged of his friendship with his Chinese counterpart Xi Jinping, but recent events point to growing stresses between Washington and Beijing.

This week, the Pentagon pulled its invitation for China to participate in maritime exercises in the Pacific, then Trump on Thursday scrapped a summit with North Korea after suggesting Xi may have exacerbated a breakdown in communications.

And all this against a backdrop of simmering trade tensions -- and a bizarre case involving a US official and a possible "sonic attack."

- Summit sunk -

Trump on Thursday scrapped the historic summit with Kim Jong Un -- set to take place June 12 in Singapore -- to discuss the "denuclearization" of North Korea.

Before he pulled the plug, Trump had suggested Xi might have played a role in a recent toughening of North Korean rhetoric.

"There was a difference when Kim Jong Un left China the second time," Trump said.

"There was a different attitude after that meeting and I was a little surprised. ... And I think things changed after that meeting so I can't say that I am happy about it."

On Monday, Trump suggested China might have prematurely eased up on enforcing economic sanctions against Pyongyang, a move that runs counter to the US leader's "maximum pressure" campaign.