The Taoiseach has taken part in a Coalition of the Willing meeting, which took place as part of ongoing diplomatic efforts aimed at ending Russia's war of aggression against Ukraine.
The Coalition of the Willing, which comprises some 30 countries supporting Ukraine, also met to intense coordination on support for the country.
The video meeting was chaired by British Prime Minister Keir Starmer and attended by Ukrainian President Volodymyr Zelensky.
French President Emmanuel Macron was also among those attending.
Ending Russia's invasion and the support of Ukraine will be the main focus of a European Council meeting on 18 December, which will be attended by the Taoiseach.
Micheál Martin said that today's meeting was an opportunity "to take stock of the state of the talks and to hear from President Zelensky on Ukraine's ongoing engagement with the US".
"The meeting discussed how the Coalition of the Willing can support these efforts and step up its assistance to Ukraine to help deliver a positive outcome in the negotiations," he added.
The Taoiseach also said that he reiterated Ireland's "full and unequivocal support" to Mr Zelensky and the assurances that Ireland will "continue to stand with Ukraine for as long as it takes".
He said: "As I made clear to President Zelensky during his historic visit to Ireland earlier this month, we want to see a just and lasting peace for Ukraine.
"A peace that respects the principles of the UN Charter and that provides guarantees for Ukraine's future security.
"This is also crucial for Europe's future security."
Meanwhile, Tánaiste Simon Harris has said that the EU is working on measures to immobilise Russian assets on "a longer-term basis".
Speaking ahead of a meeting of Eurogroup ministers in Brussels, he said that Ukraine would be a big focus of discussions and at a meeting tomorrow of EU finance ministers.
