The US Speaker of the House, Nancy Pelosi, has issued a fresh warning to the British government that there will be no trade deal with the United States if Brexit undermines the Good Friday Agreement.

She was speaking at an event in Washington last night where she presented US Congressman Richard Neal with a lifetime achievement award on behalf of Irish-American Democrats.

In her address, Speaker Pelosi highlighted the importance of protecting the peace process in Northern Ireland.

"So many Americans were a part of the Good Friday Agreement.  It represents our values and we have no intention of it being weakened in any way," she said.

Ms Pelosi, Mr Neal and other members of Congress visited Ireland, Northern Ireland and London in April. 

At the time she said there would be no US-UK trade deal in the event of a return to a hard border after Brexit and it is a warning she repeated last night.

"Our message to the British government is don't be misled into thinking there will be a UK-US trade agreement if the Good Friday Agreement is violated and that means a backstop at the border," she said.

"We delivered that message when we there and we deliver it to any visitors that come and I must say some of the British have taken it quite well."

Asked about President Donald Trump's claims that he wants to sign a trade agreement with the UK very quickly, Speaker Pelosi told reporters that there would not be any trade deal if Brexit violates the Good Friday Agreement.