Britain and the EU will work "together" to solve the Irish border issue during Brexit talks, British foreign minister Boris Johnson insisted on Friday, after the bloc's negotiators said it was London's responsibility to find a solution.

What becomes of the land border between Northern Ireland and EU member Ireland when Britain leaves the bloc in 2019 is one of the most sensitive issues in Brexit talks.

The EU's negotiation team put the ball in London's court on Thursday with a combative paper saying the solution for the Irish border problem was strictly Britain's responsibility.

But Johnson hit back on Friday, telling AFP during a visit to British troops at a NATO base in Estonia: "It's certainly a problem we can all solve together and that's what we're going to do."

People and goods currently move freely across the Irish border, but there are concerns that this cannot be sustained after Brexit, though both sides say they want to avoid a "hard" border.

"I think there is a solution and we're going to get on and do it," Johnson told AFP.

"We've had a common travel area for 100 years, nothing must affect that, nothing must affect the ability of farmers to move their stock and for businesses to get on with their lives."

The EU's chief Brexit negotiator Michel Barnier on Thursday voiced concern at London's proposal for the Irish border, insisting Brussels would not let Britain use Ireland as a "test case for future EU-UK customs relations".

In its position paper last month, London said the issue of how goods and people will move across the Irish frontier cannot be separated from discussion about wider customs arrangements between Britain and the European Union. 

The EU has refused to broach any aspect of the future trade relationship until Brexit talks had achieved sufficient progress on citizen's rights, the Irish border and Britain's financial bill to leave the EU.