Theresa May has told EU leaders she can get the Brexit deal through Parliament if they give her legally-binding changes to it.
The UK prime minister – who also vowed to deliver Brexit “on time” – was speaking after a series of meetings with top EU officials in Brussels.
European Commission President Jean-Claude Juncker again ruled out the kind of changes Mrs May wants to see.
But the two sides agreed to further talks to break the deadlock.
Mrs May said she had also spoken to European Council President Donald Tusk about his comments on Wednesday about there being a “special place in hell”for those who campaigned for Brexit without a plan to deliver it safely.
She said Mr Tusk’s language “was not helpful” and had “caused widespread dismay in the United Kingdom”.
Mrs May said she had told him he should be “focusing” on working with the UK to get a Brexit deal.
Mr Tusk tweeted that there was “no breakthrough in sight” following his talks with the UK prime minister.
Mrs May said she had “set out very clearly the position from Parliament that we must have legally binding changes to the withdrawal agreement in order to deal with Parliament’s concerns over the backstop”.
That, “together with the other work that we’re doing on workers’ rights and other issues, will deliver a stable majority in Parliament,” she said.
Mr Juncker “underlined that the EU27 will not reopen the withdrawal agreement” in their talks, according to a joint statement released by the two sides.
But he “expressed his openness” to adding words to the non-binding future relationship document – that also has to be backed by MPs – to be “more ambitious in terms of content and speed”.