China has fast become a top election issue as US President Donald Trump and Democrat candidate Joe Biden engage in a verbal brawl over who is better at playing the tough guy against Beijing.

The Trump campaign put out adverts showing Mr Biden toasting China’s Xi Jinping – even though Mr Trump did just that with the Chinese leader in Asia and hosted him at his Florida club.

Spots from the Biden campaign feature Mr Trump playing down coronavirus and praising Mr Xi for being transparent about the pandemic, even though it is clear China hid details of the outbreak from the world.

Election 2020 China
US President Donald Trump with Chinese President Xi Jinping during a meeting on the sidelines of the G20 summit in Osaka, Japan, last summer (Susan Walsh/AP)

“I think it’s going to be absolutely critical but I don’t know who is going to have the advantage,” Republican pollster Frank Luntz said.

He has been reviewing the ads and thinks China is one of the three leading issues along with the economy and the handling of the coronavirus.

“Which person looks more subservient to the Chinese leaders is the person who’s in more jeopardy,” Mr Luntz added.

As coronavirus spread throughout the US, a Pew Research Centre poll in March found Americans have increasingly negative views of China, with 66% saying they had an unfavourable opinion.

That was the most negative rating since the question was first asked in 2005.

The same poll found 62% of Americans calling China’s power and influence a major threat to the US, compared with 48% two years ago.

A NBC News/Wall Street Journal poll in late May and early June found registered voters were about evenly divided over which of the candidates would be better at dealing with China, with 43% saying Mr Trump compared with 40% for Mr Biden.

In the poll, 5% viewed the pair equally, while 10% said neither would be good.

Election 2020 China
Chinese President Xi Jinping and then-US Vice President Joe Biden walk down the red carpet during an arrival ceremony at Andrews Air Force Base in Maryland, US, in September 2015 (Carolyn Kaster/AP)

Mr Trump’s advisers see China as an opportunity to portray Mr Biden as deferential to Beijing when he was President Barack Obama’s vice-president.

The campaign made a push in May to link Mr Biden with China, complete with an advertising blitz, but the effort did little to raise Mr Trump’s poll numbers.

The Trump campaign credits the president with signing the first phase of a trade deal with China in January, which boosted stock markets and seemingly ended a bruising trade war.

More than two dozen actions the administration has taken since April to protect US jobs, businesses and supply chains from damage caused by the Chinese Communist Party’s policies have been listed by the White House.

It includes last week’s move to impose sanctions on Chinese officials for their roles in repressing religious and ethnic minorities.

That message could strike a chord with the increasing number of Americans who have an unfavourable view of the Asian power.

Meanwhile, Mr Biden’s campaign is working to portray Mr Trump as someone who talks tough but has failed to hold China accountable for its response to the virus and has signed only the first phase of a trade deal.

The campaign says while that deal was being negotiated, Mr Trump was saying Covid-19 would “miraculously” be gone in April and now it is July and cases are surging and the death toll rising.

“Trump said he’d get tough on China,” one of the Biden campaign ads says.

“He didn’t get tough – he got played.”