The United Kingdom and the EU have failed to reach an agreement on the next phase of the Brexit talks, Theresa May said.
The prime minister said the talks would resume "before the end of the week" and was "confident that we will end this positively".
Talks have collapsed after the DUP refused to accept concessions on the Irish border issue.
Downing Street said it was not the only major problem. The Prime Minister of Ireland Leo Varancar has said that an agreement has been reached, but the United Kingdom seems to have changed its mind on the Irish border issue.
"I am surprised and disappointed that the British government now does not seem to be able to reach what was agreed earlier today," he told a news conference in Dublin.