Image copyright EPA Image caption Donald Tusk chairs the group of EU national leaders

There will be no Brexit withdrawal agreement and no transition deal unless the Irish border issue is resolved, Donald Tusk has said.

Mr Tusk's role is to chair the group of EU national leaders.

Speaking in Strasbourg he said: "The UK's decision on Brexit has caused the problem and the UK will have to solve it.

"Without a solution there will be no withdrawal agreement and no transition."

Senior Brexit negotiators are due to meet on Wednesday to assess if progress has been made on Irish border issues.

The UK and EU agree there should be no hard border but differences remain on how to achieve that goal.

In March, EU leaders agreed to a 21-month Brexit transition period between March 2019 - when the UK officially leaves - and the end of 2020.

It is effectively a standstill deal which means the UK will continue to follow EU rules in that period and have unimpeded access to the single market.

Image caption All sides have agreed there should be no physical barriers along the Irish border

However, the transition period will only be implemented if there is also a deal on the Irish border.

Addressing the European Parliament Mr Tusk said there was "positive momentum" in the Brexit negotiations to finally settle outstanding issues.

Manfred Weber, leader of the parliament's largest political group, said "we stand firmly behind our Irish friends."

DUP MEP Diane Dodds said the deal reached in March was "far from perfect, not least for UK fishermen."

She added that the solution to the Irish border issue was not to create a "vastly more problematic border" between GB and Northern Ireland.

Technical talks in recent weeks have covered issues including customs, goods regulation and individuals' rights.

Transition period

Wednesday's Brussels meeting involves Olly Robbins, the prime minister's Europe adviser and Sabine Weyand the EU's deputy chief negotiator.

In March, EU leaders agreed to a 21-month Brexit transition period between March 2019 - when the UK officially leaves - and the end of 2020.

It is effectively a standstill deal which means the UK will continue to follow EU rules in that period and have unimpeded access to the single market.

However, the transition period will only be implemented if there is also a deal on the Irish border.

In December, the EU and UK agreed that the border could be kept frictionless in three possible ways:

A comprehensive trade deal

A special arrangement for Northern Ireland which could involve technology or unique customs arrangements

The so-called 'backstop' which could mean Northern Ireland or the UK as whole continuing to follow many EU rules.

In February, the EU proposed a backstop which would involve the UK, in respect of Northern Ireland, maintaining full alignment with those rules of the EU's single market and customs union which support north-south cooperation.

The UK has rejected the EU's interpretation of what the backstop means but has not yet suggested an alternative.

On Monday, Ireland's foreign minister warned that there will be "difficulties" in the Brexit process if there has not been substantial progress on the Irish border issue by June.