Prime Minister Theresa May has said Britain will play a "full and active role in the EU" until it leaves.
Following Brexit, Britain will remain "open" and "outward looking" and is committed to trading freely with other European countries, she said.
The prime minister is attending her first EU summit following the referendum.
Talks aimed at establishing a free trade deal between Canada and the EU are reported to have failed.
Canada's trade minister Chrystia Freeland announced the intense talks had broken down as she walked out of meetings with EU leaders in Belgium.
A spokesman for the European Commission said that the talks had currently halted, but they were still continuing to work on a deal.
All 28 EU governments support the Comprehensive Economic and Trade Agreement (CETA).
But the bloc cannot approve the deal without support from five sub-federal administrations, and French-speaking Wallonia has steadfastly opposed it.
Asked if she was undermining the UK position, she said: "You can't undermine something that doesn't exist."
The deal would set up a free trade zone between the EU and Canada - and could be an important test for the UK's Brexit negotiations.
European Commission President said an EU-Canada free trade deal would help end Canadian visa restrictions for Romanians and Bulgarians.