US President Donald Trump and First Lady Melania have been caught on camera having an animated discussion through the windows of the Marine One helicopter.

The footage, which has gone viral, triggered speculation of a spat similar to the plane incident involving French President Emmanuel Macron’s wife Brigitte shoving him in May.

Trump and Melania were filmed when the chopper landed on the White House’s South Lawn in Washington DC after Trump’s visit to the UN headquarters in New York.

In the video, the Trumps are seated opposite one another and are deeply involved in their discussion, with fingers and hands waving.

Melania, 55, can be seen gesticulating with her right hand as she sits upright and speaks at Trump.

Trump, 79, leans in and points towards her with his right finger while uttering something.

Afterwards, the couple exits the helicopter and walks across the lawn, with Trump waving to reporters.

The clip sparked speculation of a spat between the president and first lady.

But lip-reader Jeremy Freeman, who has been an expert witness in UK court cases, told The Daily Mail that the Trumps were talking about the so-called “escalator-gate” incident at the UN headquarters earlier in the week.

Freeman said: “From my interpretation, I don’t think Donald Trump was having a go at Melania Trump — but at the shenanigans at the UN.

Melania said of the escalator incident: “You just continued”.

Trump seemingly replied: “It was unbelievable. How can you do that?”

Freeman suggested Melania then said something like: “Donald, look at me.”

A second British lipreader, Nicola Hickling, told the outlet that Trump stated: “I can’t forgive them, they tried to hurt you.”

Melania replies: “We can’t do this, we should stay safe, you’re not safe.”

Then Trump says: “They’re done. We must challenge them”.

Trump raised the escalator incident during his hour-long speech to the United Nations General Assembly on Tuesday.

The escalator abruptly stopped shortly after Trump and Melania stepped onto it.

“These are the two things I got from the United Nations — a bad escalator and a bad teleprompter,” he told the 193-member assembly, to some laughter.

White House Press Secretary Karoline Leavitt wasn’t so lighthearted about it.

“If someone at the UN intentionally stopped the escalator as the President and First Lady were stepping on, they need to be fired and investigated immediately,” she posted on X after the incident.

But the United Nations believes it solved the mystery and said Trump’s own  videographer may have accidentally triggered a safety mechanism.

UN spokesperson Stephane Dujarric said a readout of the escalator’s central processing unit indicated it “had stopped after a built-in safety mechanism on the comb step was triggered at the top of the escalator”.

He said Trump’s videographer had been travelling backwards up the escalator to capture his arrival with First Lady Melania Trump.

“The videographer may have inadvertently triggered the safety function,” Dujarric said in a statement.

“The safety mechanism is designed to prevent people or objects accidentally being caught and stuck in or pulled into the gearing.”

The White House did not immediately respond to a request for comment on the UN findings.

On the teleprompter, Trump told the General Assembly: “I can only say that whoever’s operating this teleprompter is in big trouble.”

However, a UN official said the White House had operated its own teleprompter.

After Trump finished speaking, UN General Assembly President Annalena Baerbock said: “The UN teleprompters are working perfectly”.

-with AAP