While the coronavirus pandemic has stalled much of the world's activity, China has kept up its aggression in the disputed South China Sea — actions that analysts said could deepen the mistrust between Washington and Beijing.
China's continued hostility toward its Southeast Asian neighbors in the contested waters appear at odds with the soft power that Beijing has sought to portray as the outbreak in the mainland receded. In the past few weeks, China has sent help to countries hit hard by the pandemic and rallied for global coordination in managing the outbreak.
But the sinking of a Vietnamese fishing boat by a Chinese surveillance vessel earlier this month once again brought into the spotlight Beijing's multi-year assertions in the South China Sea, in which it claims nearly the entire waterway. Other main claimants to the resource-rich waterway include the Philippines, Vietnam, Malaysia, Taiwan and Brunei.
"Fundamentally, China has not let the Covid-19 outbreak dampen its pursuit of foreign policy issues. In addition to the South China Sea, Beijing has also authorized air force flights around Taiwan in the past month," Kelsey Broderick, China analyst at consultancy Eurasia Group, told CNBC in an email.
"China may be hoping to both send a message to other countries involved in the South China Sea that China will not back down under any circumstances, and send a message to a domestic population about the strong leadership of the party," she added.
The coronavirus, which has infected over two million people globally, first appeared in the Chinese city of Wuhan in December last year. There have been accusations both domestically and internationally that Chinese authorities ignored early warnings about the outbreak and attempted to downplay its severity.
Collin Koh, an expert on maritime security at Singapore's Nanyang Technological University (NTU), told CNBC there were "speculations" about whether the pandemic would hamper China's ability to "maintain vigil over issues of national defense and security concerns."
"This would send the wrong signal back home and to the international community — that there's a let-up in asserting such interests that concern sovereignty and rights," he said, explaining that could be why China has had to maintain its activity in the South China Sea.
"What I observe is that, since the outbreak till present, there's no rolling back at all," said Koh, a senior fellow at the S. Rajaratnam School of International Studies, a think tank within NTU.
Issues surrounding the South China Sea have for years been a point of contention in the relationship between the U.S. and China — the world's top two economies competing for geopolitical influence in Asia Pacific.
The U.S. doesn't claim any parts of the South China Sea as its own but has long promoted the "freedom of navigation" by air and sea across the waterway, which Washington has accused Beijing of militarizing.
The U.S. has conducted activities including surveillance and military exercises in the area that is also a vital commercial shipping route, where an estimated $3.4 trillion of the world's trade passed through in 2016, according to think tank Center for Strategic and International Studies.
Meanwhile, the U.S. Energy Information Administration (EIA) estimated that more than 30% of the world's maritime crude oil trade — or an estimated 15 million barrels per day — passed through those waters in 2016. Data by the EIA also showed that the South China Sea is rich in resources, containing some 11 billion barrels of oil and 190 trillion cubic feet of natural gas in proved and probable reserves can be found there.
Following the sinking of the Vietnamese fishing boat, the U.S. hit out at China, saying it's "seriously concerned" by reports of what Beijing did.
"This incident is the latest in a long string of PRC actions to assert unlawful maritime claims and disadvantage its Southeast Asian neighbors in the South China Sea," the U.S. Department of State said in a statement, referring to China's formal name, People's Republic of China.
"We call on the PRC to remain focused on supporting international efforts to combat the global pandemic, and to stop exploiting the distraction or vulnerability of other states to expand its unlawful claims in the South China Sea," the statement read.
In response, China's Ministry of Foreign Affairs accused the U.S. of sending "warships and planes to make waves in the South China Sea" and attempting to "negate China's legitimate claims and stir up troubles."
"At present, the world is in a crucial period of jointly combating the pandemic. While fighting the pandemic at home, China is doing its utmost to support and help other countries in need, which has won universal praise from the international community," said a Chinese foreign ministry spokesman Zhao Lijian.
"China urges the US to stop linking the pandemic with maritime issues and focus on domestic and international anti-epidemic response instead of doing otherwise," Zhao added.
Such an exchange could contribute to "a worsening relationship around foreign policy issues" between the U.S. and China, said Broderick of Eurasia Group.
She added that in the coming weeks, the U.S. may be "especially sensitive to China's attempts to leverage its Covid-19 aid for more leadership in international institutions like the (United Nations) or for a stronger leadership role in Asia."
Further mistrust between the U.S. and China is also unnecessary at a time when countries globally should be working together to fend off a fast-spreading coronavirus disease, said Susan Thornton, a lecturer and senior fellow at Yale University's law school.
She told CNBC's "Squawk Box Asia" that both countries should focus on getting their respective economies back on track, and set aside "other issues that are still pending."
"We don't need extraneous crises right now, we've certainly got enough on our plate with this once-in-a-century kind of global crisis that we're all facing right now," she said.
Nevertheless, China's sinking of the Vietnamese fishing vessel in a part of the South China Sea claimed by both sides reflects the ongoing tensions among countries involved in a complicated and decades-long territorial dispute.
China claims large swatches of the sea based on what Beijing said are nine dashes delineating Chinese historical territory in olden maps. The so-called "nine-dash line" overlaps with territorial claims by several parties, and forms the basis for China's actions ranging from drilling for oil to creating artificial islands in the disputed waters.
A number of claimants — including China, Taiwan, Vietnam, Malaysia and the Philippines — also contest over some islands, reefs and shoals in the South China Sea.
In 2016, an international tribunal dismissed the nine-dash line as legally baseless — a ruling that China ignored.
Koh from Singapore's NTU said a resolution to the dispute is "a long way off" even though the claimants have made some progress in negotiating a joint "code of conduct." The framework, initially aimed to finalize next year, will form the basis to manage and resolve the territorial dispute.
"However, the pandemic might have thrown uncertainties into the works. And my concern is that any of the claimants, China in particular, might simply use this window of delay to further consolidate and strengthen its position in the (South China Sea)," he said.
"And we do see now how China is already doing that."