The EU's chief Brexit negotiator Michel Barnier has said work needs to begin immediately on implementing what has been agreed on Northern Ireland.
Mr Barnier was speaking as he launched the EU's negotiating objectives for a trade deal with the UK.
He said "proper implementation" of what has been already agreed would help build confidence.
Mr Barnier added that new checks on goods entering Northern Ireland would need to be prepared for.
"When I look at the Irish protocol there you see a reciprocal commitment on the part of of Boris Johnson's government and ourselves to set up checks on goods entering Northern Ireland," he said.
The Brexit deal means that at the end of 2020 Northern Ireland will continue to follow EU rules on agricultural and manufactured goods while the rest of the UK will not.
Additionally, the whole of the UK will leave the EU's customs union, but Northern Ireland will continue to enforce the EU's customs code at its ports.
This will mean some new checks and processes for goods moving between Northern Ireland and other parts of the UK.
The nature and extent of any checks will only become clear as a result of further negotiations between the EU and UK.
Mr Barnier said he will report "regularly and publicly" on progress in implementation.
"That will be a sign of confidence and credibility for our discussions".