British Prime Minister Theresa May meets U.S President Donald Trump during the G20 summit on July 8, 2017 in Hamburg, Germany.

The Nobel Prize-winning economist Joseph Stiglitz has said it would be a "waste of time" for the U.K. to negotiate a trade deal with U.S. President Donald Trump.

Stiglitz said in an interview with the BBC that the U.K. could not put faith in a deal with Trump.

"No, I think it would be a waste of time to begin negotiations with him," he said. "If you look at what he has been putting forward as a negotiating position in the Nafta discussions you get a feeling of how much of a waste of a time it would be."

Stiglitz said that Downing Street should focus its efforts instead on the post-Brexit deal with Europe.

"Given the hurdles that the U.K. has in negotiating with the EU... I think it would be just a waste of time for you to use your scarce resources to try to have a trade deal with the United States," he added.

The U.S. is the U.K.'s second-largest trading partner outside of the EU, importing approximately 20 percent of all Britain's goods and services.

In July, International Trade Secretary Liam Fox met with U.S. Commerce Secretary Wilbur Ross to discuss prospects of a bilateral trade deal.