"Intensive" work is needed to overcome differences on the Irish border and reach a Brexit deal, Theresa May says, BBC reports.
Speaking in Brussels, where she hopes to convince her counterparts to back her plan, the UK prime minister said "considerable progress" had been made in recent weeks.
She has held meetings with key figures before addressing leaders ahead of their dinner this evening.
A senior EU official suggested Mrs May had offered "nothing new" of substance.
"There was a message of goodwill and readiness to reach an agreement, but I didn't perceive anything substantially new in terms of content," said Antonio Tajani, president of the European Parliament.
