The rising tensions between China, US

Recent events point to growing stresses between Washington and Beijing

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.

China insists it is strictly enforcing sanctions adopted by the UN Security Council.

- Pacific exercise -

The Pentagon on Wednesday withdrew its invitation for China to join maritime exercises in the Pacific because of Beijing's "continued militarization" of the South China Sea.

China hit back at the decision to disinvite it from the Rim of the Pacific exercises, calling it "very non-constructive" and saying it was taken without due reflection.

"It's also a decision taken lightly and is unhelpful to mutual understanding between China and the US," China's Foreign Affairs Minister Wang Yi said.

- Trade war -

China and the US have stepped back from a potential trade war after Beijing officials were reported to have offered to slash the country's huge surplus by $200 billion.

But no formal deals have been struck, and China has denied that any figure was set during negotiations in Washington.

Trump -- who once accused China of "raping" the US -- said he was "not satisfied" with the agreement and the issue is sure to keep grating on relations with Beijing.

- Sonic strains -

On Wednesday, the US embassy in Beijing issued a warning after reporting that an employee in the southern city of Guangzhou was diagnosed with mild traumatic brain injury (MTBI) apparently linked to "abnormal sounds."

"The medical indications are very similar and entirely consistent with the medical indications that have taken place to Americans working in Cuba," Secretary of State Mike Pompeo said.

In Cuba last year, 24 diplomats and their family members were left with mysterious injuries resembling brain trauma, which were suspected of being caused by a "sonic attack."

China said it had investigated the issue but hadn't found that any organization or individual had "carried out such a sonic influence."