The Taoiseach has said that Brexit has undermined 20 years of peace in Northern Ireland and is "fraying" relations between Ireland and Britain.
Speaking on RTÉ's Marian Finucane programme, Leo Varadkar said anything that pulls the two communities apart undermines the Good Friday Agreement.
Mr Varadkar also said he has a good relationship with DUP leader Arlene Foster.
He said the DUP and Sinn Féin need to come together and come to an agreement to get the Stormont Assembly up and running again.
The Taoiseach said if there was some clarity on Brexit in the next couple of weeks or months, there would be an opportunity to get the Executive up and running again.
He also said Ireland was entering into a potentially difficult period, even if an agreement is struck.
Mr Varadkar has also said it could be a few years before every house in Ireland has access to broadband.
The Fine Gael leader said he could not say exactly when everyone would have access to broadband, but he said the houses that would be "easiest to do" could be done in the next year or two.
He said the Government was at a very advanced stage with agreeing a broadband contract.
However, he said he could not put a definite timeframe on when the remaining 500,000 homes, farms and businesses would have access to broadband because the contract is not yet agreed.
Mr Varadkar said they would know in the next few weeks if it is possible to agree the contract.
He cautioned that if this is not possible the Government would have to have a Plan B which could take "very long and be very expensive".
The Taoiseach's Brexit comments come after a Dublin senator said a return to a hard border threatened the peace process, following reports that a backstop plan was close to being agreed with Brussels.
Senator Neale Richmond, who chairs the Seanad's Brexit Committee, told Brexiteer Tory MP Owen Paterson on BBC Radio 4's Today programme that plans for solving the border dispute using "existing practical systems" was "completely unfeasible".
Two days ago, Nobel peace prize winner and Conservative Lord David Trimble accused Mr Varadkar's government of "riding roughshod" over the Good Friday Agreement.
Mr Trimble, who helped draw up the landmark 1998 agreement which ended decades of deadly fighting in the province, claimed that the Brexit process could result in Northern Ireland ending up as part of an "effective EU protectorate".
Brexit talks have reached an impasse over the backstop, which would see Northern Ireland effectively remaining in the customs union and single market unless alternative arrangements were found to prevent a hard border.
But a deal involving an all-UK customs union in the Withdrawal Agreement, plus a separate backstop for Northern Ireland, is reported to be close to being agreed.
Additional reporting: PA