Speaking at the British-Irish Council summit in Blackpool, north-west England, the taoiseach said he came away from his meeting with the UK prime minister on a positive note, but emphasised that momentum was needed to break the deadlock.
Mr Martin offered renewed hope of a possible breakthrough in the deadlock the protocol has caused in Northern Ireland, saying the relationship between London and Dublin has recently “improved very significantly”.
He said the summit had "reinforced the importance of all of us working together on shared challenges".
Michael Gove, Britain’s levelling up secretary and intergovernmental relations minister, said talks were “cordial and constructive” and the UK government is “optimistic about the opportunities of reaching a resolution”.
Mr Martin said he and Mr Sunak agreed that there is a need to bring about a solution “in a harmonious way”.
“I think the relationship, certainly between the prime minister and I and both governments, has improved very significantly,” Mr Martin said. “And I think we’re both of a mind to ― with our colleagues in the European Union ― to get this issue resolved in a harmonious way.
“And I think the meeting over these two days has again reinforced the importance of all of us working together on shared challenges and shared issues.
“So therefore, the need to really get this issue resolved is important because we have other bigger issues also. Really significant economic challenges coming our way, we have the war in Ukraine.”
He said momentum and “substantive engagement” from Brussels and London would be vital to make that a reality.
“I must say I take away a positive perspective from last evening’s meeting with the prime minister, Rishi Sunak,” he said.
Asked for a timeline on when he thought the “significant window of opportunity” to solve the problems would close, he said “as soon as possible”. He said the fact that people in Northern Ireland have not had a functioning devolved government since May is a “real pressure point” to sort out the issues.
Mr Gove said he hopes Northern Ireland politicians, who could not join the British-Irish Council meeting owing to political deadlock in the region, will attend the next summit in the summer.
“The next British-Irish Council meeting will be in Jersey in June or July,” he said. “I sincerely hope that we have ministers from the Northern Ireland executive there then, the sooner the better.”
Mr Gove said he was optimistic about finding a resolution to the row over post-Brexit arrangements in Northern Ireland but played down any EU or Irish hopes that the controversial Northern Ireland Protocol Bill’s legislative passage would be paused.