EU leaders will gather on Thursday for a summit at which they are expected to approve the terms of a transition deal with the UK after Brexit.
The EU's Donald Tusk said on Wednesday he had recommended a draft legal text on transition, citizens' rights and other withdrawal issues to its members.
It followed Spanish concerns over how the accord would affect its demands for a say on how Brexit affects Gibraltar.
The transition is set for exit day on 29 March 2019 until the end of 2020.
Prime Minister Theresa May has said what she calls the "implementation period", in which the UK will have to adhere to EU rules, will be a bridge to a new economic and political partnership with the EU.
Under the terms of the agreement, the UK will be able to negotiate, sign and ratify its own trade deals while EU citizens arriving in the UK will enjoy the same rights and guarantees as those who arrive before Brexit.
However, a written declaration issued by the European Council on the eve of the summit noted that agreement had not been reached in some areas, including both Northern Ireland and Gibraltar.
There have been complications over the British overseas territory, which will leave the EU on the same day as the UK, in the run-up to Thursday's meeting.
At the UK's request, Gibraltar was specifically mentioned in the transition text but Spain, which maintains a long-standing sovereignty claim, subsequently sought reassurances that its interests would be protected.
Also on Friday, the EU is set to adopt guidelines for its negotiations over its future relationship with the UK.
Mrs May, who will not be present when the other EU leaders discuss Brexit, will brief her counterparts on Thursday on the poisoning of former Russian spy Sergei Skripal and his daughter in Salisbury.
The European Council is expected to adopt conclusions strongly condemning the attack, which the UK government has said the Russian state was culpable for.