Manoeuvring by a Chinese warship in the Taiwan Strait on Saturday a few days after a Chinese air force jet came dangerously close to a US aircraft was "unsafe and unprofessional", a senior National Security Council official said on Monday.
National Security Council spokesman John Kirby added that the close calls elevated tensions at a time when relations between the two major powers were already strained.
"It won't be long before somebody gets hurt," Kirby said at a regular White House briefing. "That's the concern with these unsafe and unprofessional intercepts. They can lead to misunderstandings. They can lead to miscalculations."
According to the Pentagon, a Chinese warship came within 150 yards (137 metres) of hitting the American destroyer USS Chung-Hoon over the weekend during a joint Canada-US operation.
Video footage taken from the deck of the US Burke-class Aegis destroyer released by the Pentagon appeared to show the Chinese ship cutting across the Chung-Hoon's bow, leaving a large wake and prompting the US vessel to veer to the left.
This followed claims levelled by the Pentagon that on May 26 an American Boeing RC-135, while conducting a routine mission in the region, was forced to retreat after being hit by turbulence it said was intentionally caused by a Chinese jet.
"When you have pieces of metal of that size, whether it's in the air or on the sea, and they are operating that close together, it wouldn't take much for an error in judgment or a mistake to get made, and somebody could get hurt," Kirby said. "And that's just got to be unacceptable."
The spokesman, a retired rear admiral, also decried the near complete breakdown in contact between the US and Chinese militaries since then-House Speaker Nancy Pelosi visited Taiwan last August.
Kirby said US Secretary of State Antony Blinken was still trying to arrange a visit to Beijing to restore contact, with the recent intercepts an example of why Washington "wants to be able to have open lines of communication".
"It shouldn't take the secretary of state to fly to Beijing to do that," Kirby added. "But I know he's willing to if needed."
Chinese foreign ministry spokesman Wang Wenbin said on Monday in Beijing that China's ship intercept on Saturday was a measured response to a US provocation.
"These actions are completely justified, lawful, safe and professional," Wang said. "China resolutely opposes the country concerned stirring up trouble in the Taiwan Strait."
On Sunday at the Shangri-La Dialogue in Singapore, Chinese Defence Minister General Li Shangfu said China "must prevent attempts that try to use [that] freedom of navigation, that innocent passage, to exercise hegemony of navigation".
In a press conference at the same conference, US Secretary of Defence Lloyd Austin raised the spectre of the 2001 mid-air collision between Chinese and US aircraft over Hainan Island that killed a Chinese pilot and crippled the US EP-3 spy plane.
"In those days we were talking to the PRC and it was still very difficult to manage that crisis. Imagine now if something happens and we don't have clear communications, how difficult that's going to be and what could happen in the short term," Austin said.
"As I have engaged our allies and partners here and in other places, everybody has the same desire to be able to sail the seas and fly the skies in international space. So what we continue to see from the PRC is very concerning."