Britain will more clearly explain within days how Northern Irish lawmakers can potentially veto new European Union laws, the government's minister for the region said on Friday as London tries to convince unionists to back a new deal with the EU.

Chris Heaton-Harris also said London would seek to provide assurances around Northern Ireland's place within the United Kingdom by amending legislation, a process that could take much longer and raises the prospect of a long delay before unionist politicians make up their minds.

The ultimate success of the new deal agreed on Monday to simplify post-Brexit trade rules for Northern Ireland is likely to hinge on whether it convinces the Democratic Unionist Party (DUP) to return to the region's power-sharing government.

The DUP, the largest pro-British party, has boycotted the regional assembly for over a year in protest at the original post-Brexit checks between Britain and Northern Ireland and has said it will take time to study the new agreement.

While opinion polls have consistently shown a majority of Northern Irish voters - who opposed Brexit - favoured the aim of the original trading arrangements, the checks angered many unionists who see it as undermining the union with Britain.

The deal introduced a new mechanism called the 'Stormont brake' that will allow London to stop the application of new or amended EU laws on goods in Northern Ireland if requested by a third of the region's lawmakers.

"Just to make sure that we get this exactly right, in the next few days, we're going to codify this," Heaton-Harris told BBC Radio Ulster, referring to the Stormont brake.

"We are giving time and space to the DUP and other parties to digest what's in here, we are going to clarify exactly how the Stormont brake will work and bring forward amendments to the 1998 Northern Ireland Act to absolutely demonstrate that Northern Ireland's place is in the United Kingdom." (Reporting by Amanda Ferguson, writing Padraic Halpin, editing by Robert Birsel)