US President Joe Biden has raised the issue of human rights abuses in Xinjiang during his first call with Chinese counterpart Xi Jinping, the White House said.
Mr Biden also pressed Mr Xi on trade, the clampdown in Hong Kong and ongoing tensions with Taiwan.
According to Chinese state television, Mr Xi warned Mr Biden bad relations would be a disaster for both countries.
Tensions have soared in recent times, over trade, espionage and the pandemic.
The China-US relationship is crucial to both sides and the wider world, with Beijing repeatedly calling on the new administration in Washington to improve relations which had deteriorated under Donald Trump.
The call came just ahead of the Lunar New Year, in what is being seen as a goodwill gesture.
After the call, Mr Biden tweeted: "I told him I will work with China when it benefits the American people."
In a statement, the White House said the president had "underscored his fundamental concerns about Beijing's coercive and unfair economic practices, crackdown in Hong Kong, human rights abuses in Xinjiang, and increasingly assertive actions in the region, including toward Taiwan".
China is accused by rights groups of detaining more than a million Uighurs in what the state calls "re-education camps" in Xinjiang province. There is evidence that Uighurs - a largely Muslim minority community - being used as forced labour and of women being forcibly sterilised.
China denies the reports.
What did Biden and Xi talk about in their 2-hour call?
Zhaoyin Feng, BBC News Washington
There's finally an occasion for the long-anticipated phone call between leaders in Beijing and Washington.
The two leaders are not strangers. When Biden and Xi were both vice-presidents of their countries, they met and spoke many times. Among prominent western politicians, Biden is arguably the one who has spent the most time with Xi.
It's widely seen as a good-will gesture from Washington to send well-wishes on Chinese people's most important festival. But the White House readout indicates that Biden didn't mince his words and took a hard line on the thorniest issues of the US-China relations, such as trade disputes and China's actions toward Hong Kong, Xinjiang and Taiwan.
In the readout from the Chinese side, however, the tone and focus are significantly different. Xi called for mutual respect and cooperation between the two countries, while he also pushed back by suggesting Biden "act cautiously" on the three abovementioned regions.
The diverging government statements signal that in the post-Trump era, both sides still will not budge on key issues that have been generating tensions. The Year of Ox may see deepening and widening conflicts between China and the US.
The two leaders also exchanged views on countering the Covid-19 pandemic, as well as the shared challenges of global health security, climate change and the prevention of weapons proliferation.
China's state broadcaster CCTV said that the two "had an in-depth exchange of views on the bilateral relationship and major international and regional issues".