Mr Johnson, who met the leaders of the Stormont Assembly on a visit there on Monday, insisted there would be no "unfair" prosecutions of veterans.
DUP Agriculture Minister Edwin Poots warned that the money could be subject to "conditions", possibly due to an executive obligation to generate additional income through the introduction of water fees or an increase in interest rates.
Sinn Fein vice president Michelle O'Neill is likely to be her party's nomination for deputy first minister.
Politicians from all five main parties in the province met for the first time since 2017 on Saturday, after an agreement on a new power-sharing coalition was reached.
She told the BBC: "I was very concerned about that deal in October, and I make no apologies for that". A January 13 deadline for agreement remains in place, Irish Foreign Minister Simon Coveney said on Friday, with assembly members potentially facing fresh elections if a deal isn't sealed by then.
The Irish government has also made financial pledges within the agreement to honour commitments to part-fund some north/south projects, such as the A5 dual carriageway and a redevelopment of the Ulster canal system.
The "New Decade, New Approach" deal will also be accompanied by what the UK Government has promised will be a major investment package.
Mr Johnson said discussions at Stormont would focus on how the executive meant to take forward "critical reforms" to public services.
"After three years, Stormont is once again open to business with a framework that can now move forward with improving people's lives and providing services to all communities in Northern Ireland", a- he declared.
Mr. Johnson said the discussions in Stormont would focus on how the executive would push "critical reforms" for public services.
"The parties of Northern Ireland have shown great leadership in coming together to accept this fair and balanced deal in the interests of everyone in Northern Ireland", Johnson said.
The plenary session is expected to last for three-and-a-half hours.
The assembly is set to be recalled on Friday, a development which could end a deadlock stretching back to February 2017, when it fell over who was to blame for a renewable energy initiative that spiraled far over-budget.
That row subsequently widened to take in more traditional wrangles on matters such as the Irish language and the thorny legacy of the Troubles.