The United States said Tuesday it was developing a vaccine against a deadly virus that originated in China, and urged Beijing to step up its cooperation with international health authorities.

The US government is keen to place its own teams on the ground to review the raw data and learn more about the pathogen, which has so far claimed more than 100 lives.

"We have already started at the NIH and with many of our collaborators on the developing of a vaccine," National Institutes for Health (NIH) official Anthony Fauci told reporters.

The process would take three months to start the first trial, three more months to gather data, before being able to move into its second phase.

"But we are proceeding as if we will have to deploy a vaccine," said Fauci.

"In other words, we're looking at the worst scenario that this becomes a bigger outbreak."

China was severely criticized for its handling of the Severe Acute Respiratory Syndrome (SARS) epidemic of 2002-03, which claimed hundreds of lives, mostly on the mainland and in Hong Kong.

During that health emergency, scientists had begun to develop a vaccine, but it was never deployed, Fauci said.

Passengers wear masks to protect against the spread of the Coronavirus as they arrive at the Los Angeles International Airport
Passengers wear masks to protect against the spread of the Coronavirus as they arrive at the Los Angeles International Airport AFP / Mark RALSTON

US Health and Human Services Secretary Alex Azar said the United States has offered China assistance three times in dealing with the crisis -- so far without success.

"We are urging China -- more cooperation and transparency are the most important steps you can take toward a more effective response," Azar told reporters.

"On January the sixth, we offered to send a CDC team to China that could assist with these public health efforts," said Azar.

"I reiterated that offer when I spoke to China's minister of health on Monday, and it was reiterated again via the World Health Organization's leadership today in Beijing."

China was quick to sequence the genome of the 2019 novel Coronavirus and make it public, allowing scientists around the world to develop diagnostic tools and winning praise for its efforts, including from US President Donald Trump.

Just four days ago, Trump tweeted: "China has been working very hard to contain the Coronavirus. The United States greatly appreciates their efforts and transparency."

But the new revelation by Azar raises questions about how much China has truly cooperated.

"CDC experts are standing by ready, willing and able to go immediately to China, either on a bilateral basis or under the auspices of the World Health Organization," Azar said.

This would be necessary so that "we can see raw data, raw evidence and help design the types of studies and analytics" to answer critical questions such as incubation period and whether the infection can be transmitted while patients don't have symptoms.