WASHINGTON (NYTIMES) - Tensions between China and the United States have reached the most acute levels since the countries normalised diplomatic relations more than four decades ago, with the US government's order that China close its Houston consulate being just the latest example.

In defence, trade, technology, human rights and other categories, actions and reprisals by one side or the other have escalated sharply under President Donald Trump's administration, despite his repeated expressions of admiration for President Xi Jinping of China.

The administration is even weighing a blanket ban on travel to the US by the 92 million members of China's ruling Communist Party and the possible expulsion of any members currently in the country, an action that would likely invite retaliation against American travel and residency in China.

"I think we're in a dangerous and precipitous spiral downward, not without cause, but without the proper diplomatic skills to arrest it," said Mr Orville Schell, director of the Centre on US-China Relations at the Asia Society.

The severity of the confrontation, he said, "has jumped the wall from specific and solvable challenges to a clash of systems and values".

Mr Craig Allen, president of the US-China Business Council, said he was alarmed by the increasing invective from two superpowers that together represent 40 per cent of global economic output.

"If we are yelling at each other and slamming doors, then the world is a very unstable place, and businesses are not able to plan," he said.

Here is a look at what has happened in the past few years to exacerbate the tensions:

THE CORONAVIRUS AND ANTI-CHINESE RACISM

Mr Trump and his subordinates have blamed China for spreading the coronavirus, which first emerged in the central Chinese city of Wuhan late last year.

They have repeatedly described the virus in racist and stigmatising terms, calling it the Wuhan virus, China virus and Kung Flu.

On July 4, Mr Trump said China "must be held fully accountable".

The administration also has defunded and ordered a severing of ties with the World Health Organisation, accusing it of having abetted shortcomings in China's initial response to the outbreak.

On Tuesday, the Justice Department accused Chinese hackers of attempting to steal information about American research on a virus vaccine.

For its part, China has rejected the administration's attacks over the virus and has criticised the poor US government response to the outbreak.

Chinese propagandists also have promoted the counter-theory, with no evidence, that US soldiers may have been the original source of the virus during a visit to Wuhan last October.

A SEVERE TEST OF TRADE TIES

Mr Trump won office in 2016 partly on his accusations that China was exploiting the country's trade relationship with the United States by selling the country far more than it purchased.

In office, he decreed a series of punitive tariffs on Chinese goods, and China retaliated, in a trade war that has now lasted more than two years.

While a truce was effectively declared in January with the signing of what the administration called a Phase One trade deal, most tariffs were not eased.

SHOWDOWN IN THE SOUTH CHINA SEA

The Trump administration has increasingly challenged China's assertions of sovereignty and control over much of the South China Sea, including vital maritime shipping lanes.

Just last week, Secretary of State Mike Pompeo, who has described China as a major security threat, decreed that most of China's claims in the South China Sea are "completely unlawful", setting up potential military confrontations between Chinese and US naval forces in the Pacific.

A WIDENING BATTLE OVER TECHNOLOGY

China has long been accused by successive US administrations of stealing American technology.

The Trump White House has escalated the accusations by seeking an international blacklisting of Huawei, China's largest technology company, calling it a front for China's efforts to infiltrate the telecommunications infrastructure of other nations for strategic advantage.

The company's chief technology officer, Meng Wanzhou, has been detained in Canada since December 2018 on an extradition warrant to the US on fraud charges.

Last week, Britain declared it was siding with the US in barring Huawei products from its high-speed wireless network.

EXPULSIONS OF JOURNALISTS AND OTHER MEDIA WORKERS

Accusing China's state-run media outlets of fomenting propaganda, the Trump administration sharply limited the number of Chinese citizens who could work for Chinese news organisations in the US.

China retaliated by ordering the expulsions of journalists from The New York Times, The Washington Post and The Wall Street Journal, and took other steps that suggested further impediments to American press access in China were looming.

The New York Times, concerned about the possibility of further limitations on journalists working in China, announced last week that it was relocating much of its major news hub in Hong Kong to Seoul, South Korea.

EXPULSIONS OF STUDENTS

The Trump administration has taken steps to cancel the visas of thousands of Chinese graduate students and researchers in the United States who have direct ties to universities affiliated with the People's Liberation Army, according to US officials knowledgeable about the planning.

Such expulsions portend possible further educational restrictions, and the Chinese government could retaliate by imposing its own visa bans on Americans.

SUPPRESSION OF DEMOCRATIC FREEDOMS IN HONG KONG

Last November, Mr Trump, with bipartisan support, signed legislation that could penalise Chinese and Hong Kong officials who suppress dissent by democracy advocates in Hong Kong, the former British colony and Asian financial centre that was guaranteed some measure of autonomy by China.

In May, Mr Trump said he was taking steps to end Hong Kong's preferential trading status with the US after China passed a sweeping security law that could be used to stifle any form of expression deemed seditious by China.

Chinese authorities have denounced the measures and vowed to retaliate.

REPRESSION OF UIGHUR MUSLIMS IN XINJIANG

This month, the Trump administration imposed sanctions on a number of Chinese officials, including a senior member of the Communist Party, over human rights abuses by China in the Xinjiang region against the country's largely Muslim Uighur minority.

Beijing promised retaliation against American institutions and individuals it deemed guilty of "egregious" conduct in issues concerning Xinjiang, a vast Western expanse in China where the authorities have placed one million people in labour camps and imposed intrusive surveillance on others.

OTHER LONGSTANDING GRIEVANCES: TAIWAN AND TIBET

For the Chinese government, US actions taken in the name of defending people living anywhere in China constitutes blatant interference in its internal politics - a grievance with deep-seated roots going back to its struggles with imperialist powers in the 19th century.

In May, the Trump administration approved a US$180 million (S$250 million) arms sale to Taiwan, part of a far bigger arms deal that has angered Chinese authorities, who regard the self-governing island as part of China.

Another longstanding source of Chinese anger is the US deference to the Dalai Lama, the spiritual leader-in-exile of Tibet, the former Himalayan kingdom in China's far west.

In 2018, Mr Trump signed a Bill that penalises Chinese officials who restrict US officials, journalists and other citizens from going freely to Tibetan areas.

Last November, the State Department's ambassador-at-large for international religious freedom, Mr Samuel Brownback, warned that only Tibetans could choose the successor to the Dalai Lama, who turned 85 this month, setting up a new clash with Beijing, which contends it will choose his successor.