BEIJING -- China on Tuesday welcomed a virtual meeting between President Xi Jinping and U.S. President Joe Biden as raising hopes for better relations, while the U.S. was more muted on the talks as the world's two biggest powers sought to ratchet down more than a year of tensions.

The leaders appeared to put aside the language of acrimony in their first formal meeting since Biden took office. Xi greeted the U.S. leader as his "old friend," and Chinese Foreign Ministry spokesperson Zhao Lijian said the exchange was candid and constructive.

"If China-U.S. relations cannot return to the past, they should face the future," Zhao said, calling the meeting "conducive to increasing positive expectations ... for U.S.-China relations."

However, both sides held firm to their positions on the issues that divide Washington and Beijing, with Xi warning that the U.S. and Taiwan are playing with fire over the self-governing island that China considers part of its territory.

The two nations were aiming to end a sharp deterioration in relations that accelerated under former U.S. President Donald Trump and had festered since Biden became president in January. The video conference, which lasted more than three hours, took place Tuesday morning in Beijing and Monday evening in Washington.

Both Biden and Xi seemed determined to lower the temperature in what for both sides is their most significant -- and frequently turbulent -- relationship on the global stage.

"As I've said before, it seems to me our responsibility as leaders of China and the United States is to ensure that the competition between our countries does not veer into conflict, whether intended or unintended," Biden told Xi at the start of the meeting.

The White House set low expectations for the meeting, and no major announcements were made. Still, White House officials said the two leaders had a substantive exchange.

Xi echoed Biden's cordial tone in his opening remarks, saying, "China and the United States need to increase communication and cooperation."

The positive tone sets an example for officials in both countries to try to identify common ground rather than find fault with each other, whether on trade, climate change, or geopolitical issues such as Afghanistan and North Korea, said Wang Huiyao, president of the Center for China and Globalization, a think tank in Beijing,

"I see this dialogue as a stabilizer of the bilateral relation," he said. "I don't expect this one summit to bring us back to the good old days, but certainly it stops the downward spiral."

The two leaders had an extended discussion on Taiwan, the U.S. said. Tensions have heightened as China has recently dispatched a growing number of fighter jets toward the island, while the U.S. and its allies sail warships though the Taiwan Strait.

Xi blamed the tensions on Taiwan seeking U.S. support to achieve independence and some on the American side using Taiwan to contain China, a Chinese statement on the meeting said.

"Such moves are extremely dangerous, just like playing with fire. Whoever plays with fire will get burnt," the statement said.

White House national security adviser Jake Sullivan said Biden reminded Xi that he voted as a senator for the Taiwan Relations Act that went into effect in 1979, legislation that shapes the parameters of the U.S.-Taiwan relationship.

"So he understands deeply, firsthand, that the act makes clear that any effort to shape Taiwan's future by other than peaceful means is of grave concern to the United States," said Sullivan, speaking at a webinar hosted by the Brookings Institution, a Washington think tank, on Tuesday.

Chinese military forces held exercises last week near Taiwan in response to a visit by a U.S. congressional delegation to the island.

The White House said Biden reiterated the U.S. will abide by its longstanding "One China" policy, which recognizes Beijing as the government of China but allows informal relations and defence ties with Taipei. Biden also made clear the U.S. "strongly opposes unilateral efforts to change the status quo or undermine peace and stability across the Taiwan Strait," a White House statement said.

It said that Biden again raised concerns about China's human rights practices and made clear that he sought to "protect American workers and industries from (China's) unfair trade and economic practices." The two also spoke about regional challenges, including North Korea, Afghanistan and Iran.

The meeting could put ties on a more stable footing in the near term, but the two countries have yet to address the long-term structural challenges in their relationship, said Paul Haenle, a former U.S. official and China expert at the Carnegie Endowment for International Peace.

"This really was just an opportunity for the two leaders to make clear their intentions and priorities and concerns about their relationship and to begin really to set the terms of what is a new era in U.S.-China relations," he said.

The U.S. president was joined in the Roosevelt Room for the video call by Secretary of State Antony Blinken and a handful of aides. Xi, for his part, was accompanied in the grand East Hall of the Great Hall of the People by a number of advisers.

The high-level diplomacy had a touch of pandemic Zoom meeting informality as the two leaders waved to each other once they saw one another on the screen. Biden would have preferred to meet Xi in person, but the Chinese leader has not left his country since the start of the coronavirus pandemic.

Both leaders gave nods to their history with the other. Biden noted that the two have spent an "awful ... lot of time" speaking to each other over the years, and have never walked away "wondering what the other man is thinking."

Xi, who referred to Biden as his "old friend" when the then-vice president visited China in 2013, seemed interested in reviving the earlier days of their relationship, saying, "I am very happy to see my old friend."

But the public warmth has cooled now that both are heads of state. Biden bristled in June when asked by a reporter if he would press his old friend to cooperate with a World Health Organization investigation into the coronavirus origins.

Despite the tensions, there have been moments of progress in recent months.

Last week, the two countries pledged at UN climate talks in Glasgow, Scotland, to speed up action to rein in climate-damaging emissions.

The White House has said it views cooperation on climate change as something the two nations should cooperate on despite their differences on other issues.

"None of this is a favor to either of our countries -- what we do for one another -- but it's just responsible world leadership," Biden told Xi. "You're a major world leader, and so is the United States."

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Madhani reported from Washington. Associated Press journalists Colleen Long in Washington and Emily Wang and Joe McDonald in Beijing contributed