Many details have not yet been worked out and further negotiations are expected.
EU leaders have agreed that the post-Brexit locations of key bank and medical agencies currently based in London would be decided by November.
A series of small-scale attacks has left Europeans trying to balance their desire not to give in to extremism with a persistent anxiety that it could strike at any time.
Talks on Britain leaving the European Union began Monday with both sides saying they will focus first on an orderly withdrawal.
EU officials do acknowledge that the agreements to be reached before Britain leaves in March 2019 can only be concluded as a whole package simultaneously.