The phone conversation between the leaders came after the Group of 20 major economies pledged solidarity to contain the outbreak, which has infected 525,000 people and killed more than 23,600 people worldwide.

However, relations between China and the US have been on a downward trajectory, with each side blaming the other for a slow response to the crisis and US officials referring to the coronavirus that causes the disease as a “Chinese virus”.

Observers said the more positive atmosphere might not last long, citing the other causes of tensions in their relationship and arguing that officials might continue to play the blame game.

Liu Weidong, a specialist in US-Chinese relations from the Chinese Academy of Social Sciences, said the phone conversation would not change the decline in the two sides’ relationship.

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“Other than the temporary cooperation on curbing the pandemic, Trump did not actively respond to Xi’s call for stronger ties between the two nations, and this is an alarming sign, since Trump might take advantage of the pandemic to exert more pressure on China for strategic needs,” Liu said.

But he added: “The incendiary remarks from both nations are expected to stop after this call.”

After the talks, Trump tweeted that the conversation had been“very good”.

“Discussed in great details the CoronaVirus that is ravaging large parts of our Planet. China has been through much and has developed a strong understanding of the Virus. We are working closely together. Much respect!” he wrote.

For his part, Xi told Trump that China had been transparent and responsible in its release of information, including the gene sequence of the coronavirus, since the start of the outbreak, and had given help to other nations, according to state broadcaster CCTV.

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In a veiled swipe at US officials, including Trump, for making repeated references to “the Chinese virus” or “Wuhan virus”, Xi said: “The virus knows no boundaries and ethnicity, and it is our common enemy. The international community can only defeat it through working together.

“The relationship of China and the US is at a critical juncture. Cooperation is mutually beneficial to both nations, while fighting will hurt. Cooperation is the only correct choice.

“It is hoped that the United States will take concrete actions to improve China-US relations, and the two sides will work together to strengthen cooperation in areas such as epidemic control,” he said.

Xi said he was concerned about the outbreak in the US and health officials from the two sides were in constant communication.

“China is willing to continue to share information and experience with the United States without reservations,” he said.

The relationship between China and the US has hit the lowest point in decades with the expulsion of American journalists from China in retaliation for US restrictions placed on Chinese media organisations and a Wall Street Journal commentary with a headline Beijing deemed to be racist.

Adding to the tension, officials from the two nations have been exchanging barbs. The US has criticised China, where the outbreak was first reported, for its slow initial response and attempts to silence people who raised the alarm about Covid-19.

But Beijing has said it informed the US in early January. Trump also angered Beijing by referring the “Chinese virus” after weeks of criticism that it was racist.

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Chinese diplomats have also promoted an unproven conspiracy theory that the virus may have been brought to China by the US Army during military games in Wuhan, while their US counterparts have accused China of ordering virus samples to be destroyed in early January.

The tensions only calmed down when Trump stopped using the term “Chinese virus” this week and China’s ambassador to the US said it was “crazy” to spread rumours about the coronavirus originating from a US military laboratory.

Chin-hao Huang, an assistant professor of political science at Yale-NUS College in Singapore, said the timing of the phone call was not a coincidence.

“It’s rather strategically timed. The call came at this pivotal period where we see that the US has surpassed the number of confirmed cases in China, so that’s I think a pretty big deal,” he said.

Calculations by Johns Hopkins University show that the US has 85,996 infections, overtaking mainland China’s official tally of 81,340, although the accuracy of that figure has been questioned.

“You have the two largest economies in the world now also, the two largest countries with the highest number of confirmed cases — for the call to take place at this time, it's a bit of a symbolic gesture, ‘we’re in this together’,” Huang said.

“I think the decision to move beyond that blame game is probably signalling that both sides realise that there’s still a lot of work ahead, not just on the pandemic side.”

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Xi and Trump both attended the G20 online special meeting on Thursday to discuss the pandemic with other world leaders. In a joint statement released after the meeting, the 20 countries pledged to “spare no effort, both individually and collectively” to protect lives; safeguard people’s livelihoods; protect financial stability and revive growth; minimise disruption to trade; provide help to all countries in need; and coordinate on public health measures.

The leaders also agreed to inject US$5 trillion into the global economy.

Liang Yunxiang, an international relations specialist from Peking University, said the phone call between Xi and Trump sent out a positive signal to the international community.

“China and the US are locked in a blame game and a war of words recently, bringing uncertainties to the world. And this call, at least on the surface, emphasised cooperation and engagement, which will help stabilise the world by making a gesture that the two countries won’t end up fighting,” said Liang.

“However, there were many deep-seated problems before the pandemic started, and these problems are expected to last no matter what Xi and Trump said in the phone call. In this sense, the call can only be seen as a ‘tactical truce’ between Beijing and Washington.”

Wang Yiwei, a professor of international relations at Renmin University of China in Beijing, echoed Liang’s view and said China and the US need to find more “converging interests” to prevent their relationship becoming even rockier in the future.

Additional reporting by Kristin Huang and Sarah Zheng