United States Secretary of State Antony Blinken told the Reuters Next conference on Friday that Chinese leaders should think carefully about their actions towards Taiwan, warning of "terrible consequences" if China precipitates a crisis across the Taiwan Strait.
In an interview, Mr Blinken addressed multiple foreign policy challenges facing the administration of US President Joe Biden, including faltering efforts to repair the 2015 Iran nuclear deal, Russia's military build-up near Ukraine, and the spiralling conflict in Ethiopia.
Most acute may be China's increasingly aggressive posture towards Taiwan, which Beijing claims as its territory. Taiwan's Defence Minister has said tensions with China are at their worst in more than 40 years, adding that China will be capable of mounting a "full-scale" invasion by 2025.
Asked if China was going to invade Taiwan, Mr Blinken said, "that would be a potentially disastrous decision", repeating Washington's position that it is "resolutely committed" to making sure Taiwan has the means to defend itself.
China had been trying to change the status quo across the Taiwan Strait in recent years by engaging in provocative military manoeuvres and trying to isolate Taiwan from the rest of world, Mr Blinken said.
"I hope that China's leaders think very carefully about this and about not precipitating a crisis that would have I think terrible consequences for lots of people and one that's in no one's interest, starting with China," Mr Blinken said.
China remains Mr Biden's No. 1 foreign policy priority, but his administration has also been buffeted by crises elsewhere.
Mr Blinken said the US had sanctions it could use for parties perpetuating Ethiopia's conflict.
On Iran, Mr Blinken said Washington ended indirect talks in Vienna this week because Teheran did not seem serious about a return to compliance with the nuclear deal.
"If the path to a return to compliance with the agreement turns out to be a dead-end, we will pursue other options," he said.
Mr Blinken returned on Thursday from Europe, where he met Russian Foreign Minister Sergey Lavrov and delivered a warning over Russia's military build-up near Ukraine.
Mr Biden is expected to speak to President Vladimir Putin in the near future, and will tell the Russian leader that Washington is determined to stand up against any "reckless or aggressive" actions, Mr Blinken said. The US wants a more predictable relationship with Russia, he said.
"There are areas where we have overlapping interests and we should be able to work together if we can have some stability and predictability in the relationship. Russia's actions and the threat of further aggression against Ukraine moves in exactly the opposite direction," Mr Blinken said.