Tánaiste Micheál Martin has said clarity is urgently needed over the costs of building Casement Park.
Mr Martin spoke ahead of a meeting with new Northern Ireland Secretary Hillary Benn at Hillsborough Castle on Thursday.
There has been mounting speculation that the stadium is set to be axed as a venue for the European Championship in 2028.
The derelict west Belfast GAA ground has been earmarked for five matches in the Euros, which is being hosted in four years by the UK and Ireland.
However, the funding required to rebuild the stadium in time for the tournament is still not in place, prompting concerns that the delays will see Belfast missing out on the tournament.
Speaking to reporters ahead of Thursday’s meeting, Mr Martin said the Irish government has allocated 50 million euro (£42 million) towards the project.
Asked if he wanted to see the UK government match that investment, Mr Martin said: “It will be important that there is clarity over the costs involved and what is the overall target that’s required to bring this to realisation in time for the Euros.
“Also, then, to work out the methodology to achieve that.”
Mr Benn has said he is urgently looking at the issues around cost and remaining time for constructing the stadium, while characterising it as a “very important project”.
Meanwhile, Mr Martin said he is positive and optimistic about future Irish relations with the UK.
He also suggested there could be a “friendly settlement” to the interstate case which Ireland took against the UK over the controversial Legacy Act aimed at addressing the north’s troubled past.
He said he expected a “wide-ranging” discussion, including the stability of the Stormont Assembly and the opportunity to reset British/Irish relations.
Mr Martin said they had had a “very good phone call” last week following the UK General Election, which saw a Labour landslide win.
“We know each other. We have a good understanding of each other’s perspective, British/Irish relations and how to advance reconciliation in Northern Ireland,” he said.
There has been tension between the UK and Irish administrations in recent years following Brexit as well as the Conservative government’s controversial legacy bill.
Asked for his view on the British/Irish relationship going forward, Mr Martin said he is “positive and optimistic about the future relationship between the British and Irish governments”.
“But also I realise the challenges and I’m realistic in terms of how we meet those challenges, but what I am particularly focused on is to re-establish both governments working hand in hand as anchors of the Good Friday Agreement into the future.
“I think progress was made under Prime Minister Sunak and former secretary of state Chris Heaton-Harris in many areas, particularly in terms of the Windsor Framework, but I do believe we have an opportunity to advance the situation on a wide range of issues, to deal with the legacy issue on an amicable basis, to work through that.
“I am positive and I believe there are opportunities here the British and Irish governments can exploit, and I am confident that if we work together we can advance reconciliation, which is my key agenda in the time ahead.”
Asked whether the Irish government intends to continue an interstate case against the UK over the Legacy Act, Mr Martin said he and Mr Benn will “explore the issue”.
“There are mechanisms within the framework of the case which allow for, if you like, a friendly settlement but that will obviously depend on how the British Government is going to deal with that Legacy Act and the core issues,” he said.
“Above all, we believe the pressing issue on legacy is to restore trust in the legacy framework for the victims and families of those who lost their lives in atrocities.
“It is about the families, the survivors and victims.
“We have to restore trust.”
