The US and Chinese leaders have warned each other over Taiwan during a phone call that lasted more than two hours.
President Joe Biden told his Chinese counterpart, Xi Jinping, that the US strongly opposed any unilateral moves to change the island's status.
But he added that US policy on Taiwan had not changed.
Beijing said Mr Xi had told Mr Biden to abide by the one-China principle, warning him that "whoever plays with fire will get burnt".
Tensions over the issue have increased ahead of a rumoured plan for US House of Representatives Speaker Nancy Pelosi to visit Taiwan.
The state department says Ms Pelosi has not announced any travel, but China has warned of "serious consequences" if she were to proceed with such a visit.
Last week, Mr Biden told reporters "the military thinks it's not a good idea", but his White House has called Chinese rhetoric against any such trip "clearly unhelpful and not necessary".
Ms Pelosi, who is next in line to the presidency after the vice-president, would be the highest-ranking US politician to travel to Taiwan since 1997.
During Thursday's phone call, Mr Biden and Mr Xi also discussed arranging a possible face-to-face meeting, a senior Biden administration official said, describing the bilateral as "direct" and "honest".
When Mr Biden was US vice-president he hosted Mr Xi during a visit to the US by the Chinese leader in 2015, but they have not met in person during Mr Biden's presidency.
China sees Taiwan as a breakaway province that must become a part of the country – and has not ruled out the possible use of force to achieve this.
Under the one-China policy, Washington does not recognise Taipei diplomatically. But the US does sell weapons to the democratically self-governed island so that it can defend itself.
The White House said that apart from Taiwan, the two leaders discussed a range of other issues, including climate change and health security.
The Biden administration has been considering whether to lift Trump-era tariffs on Chinese imports, arguing that such a move could ease soaring US inflation. But the US president did not discuss that issue with Mr Xi on Thursday, the senior US official said.
Analysts believe that both Joe Biden and Xi Jinping want to avoid an open conflict, the BBC's State Department Correspondent Barbara Plett Usher reports. But neither has made any attempt to alter their competing narratives, which was illustrated again by their contrasting statements about Thursday's call.
In a brief summary, the White House said it was part of efforts to "responsibly manage differences" and work together where "interests align".
In a much longer one, Beijing said many of their interests did align. But it blamed the US for the deteriorating relationship, criticising the Biden administration's view of China as a "primary rival" and Washington's "most serious long-term challenge."
By Rupert Wingfield-Hayes, Taipei
Much is being made of the fact that President Xi told President Biden that "those who play with fire will get burned".
It is a strong warning to America – but is not unprecedented. China's foreign ministry used exactly the same language when a US congressional delegation visited Taiwan earlier this year. The same phrase was used by China's defence ministry in a warning to Taiwan last year.
The fact that it has now been used by President Xi does give it more weight.
But it doesn't mean China is preparing military action against Taiwan, if – for example – Nancy Pelosi arrives here next week. It is instead telling America that if it continues down the current path, it will eventually lead to conflict.
It's difficult to see anything positive from this phone call in terms of the wider US-China relationship.
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