US Special Envoy to Northern Ireland Mick Mulvaney has welcomed the latest Brexit developments.

Referring to the agreement on the Northern Ireland Protocol, Mr Mulvaney tweeted: "This certainly seems like good news ... and good news is always welcome."

In September, while visiting Ireland, Mr Mulvaney said that the entire federal government was agreed that if there is a return to a hard border on the island of Ireland then any potential trade deal with the UK will not go ahead.

He told RTÉ News at the time that the US would do whatever it could to prevent a return to a hard border and to protect the Good Friday Agreement.

Senior Democrats on Capitol Hill have also issued warnings there will be no US-UK trade deal if Brexit threatens the Northern Ireland peace process.

The Chairman of the House Ways and Means Committee, Congressman Richard Neal, has welcomed the latest developments.

"I strongly welcome the agreement reached between the UK and EU on the Northern Ireland protocol and encourage both sides to continue to work together on a deal which would be beneficial to all, including the people and businesses on the island of Ireland," he tweeted.

There was also reaction from the US Senate.

Democratic Senator Bob Menendez said that the Northern Ireland protocol remains essential and attempts to erode it will impact the US Senate's views on trade with the UK.

"The protection of the Good Friday Agreement and any future US-UK Free Trade Agreement are directly linked," he tweeted.

Last month, US President-elect Joe Biden stressed the importance of maintaining an open border on the island of Ireland, post-Brexit.

"We do not want a guarded border, we've worked too hard to get Ireland worked out," he told RTÉ News.