Chinese security officials blocked the US military aide carrying the briefcase that carries the procedures and communications equipment that allow the US leader to launch nuclear missiles as the official entered the Great Hall, according to the Axios news website.

Then there was a commotion as Kelly got all the US officials accompanying the president to move toward the site of the nuclear football, Axios said, citing five unnamed sources familiar with the events.

A Chinese security official "grabbed" Kelly, who "shoved" the man's hand off of his body, according to Axios, which said a US Secret Service agent then tackled the Chinese official to the ground.

The Secret Service denied the website's characterization of the events.

"FACT CHECK: Reports about Secret Service agents tackling a host nation official during the President's trip to China in Nov 2017 are false," it said on Twitter.

In a separate statement, the presidential law enforcement agency provided further details about the incident.

"An individual, not part of the official delegation, attempted to prevent one of our protectees from entering a room," it said.

"A US Secret Service agent quickly intervened and a short scuffle ensued."

However, the Secret Service added, "the individual complied with the agent's directions and no further action was necessary. At no time did anyone involved fall to the ground. The event continued without incident."

Axios reported that US officials who learned about the incident were told to keep the information to themselves, adding that the Chinese did not have the nuclear football with them at any point or touch the briefcase at all.

The head of the Chinese security detail apologized to the Americans for the misunderstanding after the incident, it added.

The nuclear football bag, aluminum-framed and weighing 45 pounds (20 kilograms) goes everywhere the president goes, carried by a military aide.

The football has been omnipresent with the leader of the world's most powerful nation since around 1963, according to Smithsonian magazine.

It has to stay close to the president, given that he would have less than five minutes to react before nuclear missiles launched at the United States by, say, China or Russia, strike.