Prime Minister Boris Johnson has arrived at Stormont to mark the restoration of devolution in Northern Ireland.
Taoiseach (Irish prime minister) Leo Varadkar is due later on Monday.
On Saturday, a new power-sharing government was formed by Stormont’s five main parties.
They agreed a deal with the governments that includes extra funding for Northern Ireland, but the exact figure is not yet known.
Mr Johnson and Mr Varadkar are due to meet the first and deputy first ministers to discuss the new executive’s priorities.
Ahead of the trip, Mr Johnson described it as a “historic time” for people in Northern Ireland.
“I look forward to meeting with the new executive and hearing about their plans for the future, including driving forward much needed reforms to public services and resolving the current health strike.”
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The deal – entitled New Decade, New Approach – was reached on Friday after months of negotiations between the parties and the two governments.
Stormont’s power-sharing coalition, led by the DUP and Sinn Féin, had collapsed in January 2017 after a row over a green energy scandal.
The return of devolution means the executive can now take decisions that had been stalled due to the three-year absence of ministers.
On Sunday, newly appointed finance minister Conor Murphy said the British and Irish governments must deliver the “promised financial package”.
He reiterated that on Monday when he told the BBC’s Good Morning Ulster programme that the parties have “delivered on their end of the bargain” and that “we need to nail down exactly what that level of commitment is”.
He said more than £1.5bn was needed.
“I spoke to the secretary of state last night and I spoke to department officials over the weekend and we are having costings done, so I hope this morning to be in a position to be able to share with executive colleagues what the cost of the commitments made in the document would be and I think that’s the figure that we will be asking the prime minister and the secretary of state to deliver,” he said.
First Minister Arlene Foster said there is a need to ensure that we have resources for a number of years so “we don’t face a cliff edge”.
“As well as that, we need to have capital investment, we have a huge hole in our infrastructure, particularly in our water infrastructure, that we need to fix,” she said.
Deputy First Minister Michelle O’Neill tweeted that domestic water charges will not be introduced in Northern Ireland.
All five main parties – the DUP, Sinn Féin, Alliance, the SDLP and the UUP – have joined the executive.
The legislative assembly’s 90 members held their first sitting on Saturday, during which new executive ministers were appointed.
The executive is expected to hold its first meeting on Tuesday, the same day that the new chairs of Stormont’s scrutiny committees are likely to be chosen.