Boris Johnson told U.S. Vice President Mike Pence that Britain was 'not keen on that chlorinated chicken' | Peter Summers/Getty Images Boris Johnson to US: Britain ‘not keen on that chlorinated chicken’ UK PM says NHS won’t be part of any transatlantic trade deal.

The National Health Service is not up for grabs as part of any trade deal between the U.K. and U.S., Prime Minister Boris Johnson told U.S. Vice President Mike Pence on Thursday.

Johnson also said Britain was "not keen on that chlorinated chicken," according to the Daily Mirror. Johnson was referring to the American practice of washing chicken carcasses with chemicals to tackle pathogens such as salmonella and E. coli — a process known as “pathogen reduction treatment” that's banned in the EU.

In a heated debate on Brexit on Wednesday, Johnson said: "There’s only one chlorinated chicken that I can see in this House, and he’s on that bench." He repeated the line to Pence on Thursday, saying: “We have a gigantic chlorinated chicken of our own on the opposition benches.”

The role of the NHS in any post-Brexit trade deal is a sensitive subject in Britain. During his state visit in June, Donald Trump said in a press conference alongside then Prime Minister Theresa May: “When you’re dealing in trade everything’s on the table, so NHS or anything else … everything will be on the table, absolutely."

A day later, he rowed back, telling ITV: “I don’t see it [the NHS] being on the table. Somebody asked me a question and I say ‘everything’s up for negotiation’ because everything is — but that’s something that I would not consider part of trade. That’s not trade.”

Johnson and Pence met in Downing Street Thursday as part of the U.S. vice president's European tour. Pence stood in for Trump in Poland at a ceremony marking the 80th anniversary of the start of World War II, as Trump stayed behind to concentrate on Hurricane Dorian. Pence also traveled to Ireland and was criticized for staying in a Trump property in Doonbeg, on the opposite side of the country from Dublin.