Finding a solution for the Irish border in Britain's talks to exit the European Union is not "beyond the wit of man", British Foreign Secretary Boris Johnson said.
"I think we can all work together to come up with a solution on that one. It is not beyond the wit of man.
"We've had a common travel area between the north and the south of Ireland for getting on for a century and we're going to continue to make that work," Mr Johnson told reporters in Estonia's capital Tallinn, where he was attending a meeting of EU foreign ministers.
Minister for Foreign Affairs Simon Coveney said Ireland cannot accept a hard border with Britain after Brexit, saying it would threaten the peace process.
He said the UK's proposals to avoid a hard border so far are unconvincing.
We cannot have a physical border on the island of Ireland again that creates barriers between communities, that will create tension, that will undermine the peace process that has taken 30 years to build.
The EU's chief Brexit negotiator said yesterday he was worried by Britain's plans for the border arrangement with Ireland.
Michel Barnier said he was concerned over the UK government's position on Ireland, which appeared to envisage the EU suspending the application of its laws, single market and customs union at a new external border.
Negotiations to extricate Britain from the EU have seen a slow start and Brussels has repeatedly warned that time is running out to answer complex and thorny questions before Britain is due to leave in March 2019.
But asked if he was confident that Brexit minister David Davis would get a deal with the EU, Mr Johnson said: "Absolutely, with rock solid confidence."
He also reiterated London's stance - firmly rejected by the EU - that the divorce talks should run together with discussion about the post-Brexit relationship between Britain and the EU.
The bloc, which will have 27 member states after Brexit, wants to solve key exit issues before opening talks about any future trade cooperation with Britain.
But, with slow progress on agreeing Britian's divorce bill, ensuring expatriates' rights and deciding on the Irish border, the EU now doubts it would give a green light in October for starting talks about the post-Brexit order, as had been planned.
Mr Johnson disagreed, saying the legal clause for leaving the EU, or Article 50, did mention taking into account a future relationship with the departing country.
"Article 50 makes it very clear that the discussion about the exit of a country must be taken in context with discussion of the future arrangements. And that's what we're going to do," he said.
Latest Brexit negotiations a qualified disappointment - Hogan
Meanwhile, EU Agriculture Commissioner Phil Hogan has described the latest round of Brexit negotiations as a qualified disappointment.
Addressing 400 delegates of the Agriculture Science Association in Naas, Co Kildare Mr Hogan said that Brussels and nationals capitals throughout Europe understand very well that Brexit is already having a negative impact on the value of Irish Agri-food exports.
He said €650 million has so far been wiped off the value of Irish food exports due to the fall in the value of sterling.
The commissioner said that in his view the European Commission and the UK need to do much more when it comes to the potential political impact that Brexit can have on Ireland.
He said that it is contradictory for the UK to say that it wants to have a frictionless border in Ireland while at the same time leaving the Customs Union and the Single Market.
Mr Hogan said the UK is responsible for this issue, that they voted to leave the European Union, and that the EU will be putting all the pressure it can on the UK to find a solution.
He said that in his opinion the UK has not yet accepted that their proposal to use a technological and economic approach to operate a frictionless border between the Republic and Northern Ireland will not work.
Mr Hogan said that he is satisfied that Ireland's political, agricultural, and business leaders are doing everything they can to protect Ireland's interests at this sensitive time. However, he said we need to keep repeating that Ireland remains 100% committed to our future in Europe.
He also said we need to solidify our position within the single market and continue building alliances with third countries especially for the key agri food export sectors.
Mr Hogan said that this is the best way to offset any Irish economic losses incurred by Brexit.