Lithuanian President Dalia Grybauskaitė is Thursday leaving for Brussels where she and other EU leaders will decide on a new phase of talks on the United Kingdom's withdrawal from the bloc.
The European Council is expected to give the green light on Friday for a second phase of talks after London last week reached a deal with Brussels on Britain's divorce bill, the rights of EU migrants and the Irish border.
However, tensions have been caused by comments by Britain's Brexit Minister David Davis that the agreement was a "statement of intent" rather than "legally enforceable."
The UK is likely to leave the EU in the spring of 2019. Before that, it expects to reach a post-Brexit trade deal with the bloc.
A priority for Lithuania in Brexit talks is to ensure the rights of several hundred thousand Lithuanians living in the UK.
The European Council will also discuss economic and defence integration. Ministers from 25 EU member states taking part in the Permanent Structured Cooperation on defence (PESCO) initiative last Monday approved a list of 17 projects including a Lithuania-led project to create cyber rapid response teams.
The EU leaders are also expected to agree on extending sanctions against Russia over its involvement in the conflict in Eastern Ukraine.