Speaking on CNBC, the reporter asked Liam Fox whether he was breaking the law and discussing a future trade relationship before the UK has exited the EU.
Mr Fox laughed off the accusation as he insisted that he was in the US to discuss trade that was already taking place between the Britain and America.
The Trade Secretary highlighted the “enormous” mutual importance of trade between the UK and US.
The CNBC reporter asked Mr Fox “what was the point” of his trip to the US as a future deal cannot be discussed until after Brexit talks.
He said: “What is the point of your current trip because EU law restricts you from starting trade negotiations until Britain has actually left the European Union.
“Are you breaking those laws at the moment?”
Mr Fox insisted that he was not in the US to discuss a future trade relationship but instead to talk about current trade between the nations.
He replied: “Well trade negotiation is one thing and actual trading is another.
“Of course the trade in goods and services last year between the United State and the UK was about $250billion, up eight per cent on the year before.
“Which is remarkable given the slow down in the rate of growth in global trade.
“We also are huge investors… we each empty through our companies about a million people in one another countries.
“So what happens in the United States to business conditions here and what happens in the Untied Kingdom are of enormous mutual importance.”
The UK formally began Brexit negotiations with the European Union on Monday over three months after Article 50 was triggered.
After welcoming David Davis with warm words, the EU negotiator, Michel Barnier told reporters: “Today we are launching the negotiations on the orderly withdrawal of the UK from the EU.
“Our objective is clear, we must first tackle the uncertainties caused by Brexit. First for citizens, but also for the beneficiaries of the EU policies and for the impact on borders, in particular, Ireland.
“I hope that today we can identify priorities and a timetable that would allow me to report to the European Council later this week that we had a constructive opening of negotiations.”