The EU is expected to appeal against a decision by the European Court of Justice (ECJ) to temporarily remove Hamas from its blacklist of terror organisations.
European foreign ministers decided at a meeting to "appeal the judgement regarding Hamas remaining on the EU terrorist list," spokesperson Susanne Kiefer said.
In December 2014, the ECJ took the Palestinian Islamist group off the terror list to give the EU a window of time to rebuild a stronger case against Hamas.
A Hamas petition to the European court of human rights (ECHR) had argued that the EU designated the Palestinian militant group a terror organisation based on the information provided by the US.
EU regulations require that the bloc uses its own evidence to categorise terrorist organisations.
The ECJ argued that the decision to put Hamas on the terror list was based on "factual imputations derived from the press and internet" not "sound legal judgement".
Hamas, which rules the occupied Gaza strip, was added to the EU's list of terror organisations in 2003 after a diplomatic bid led by Israel and the US.
EU officials have claimed that their stance towards the group has not changed.
"The Court stresses that those annulments, on fundamental procedural grounds, do not imply any substantive assessment of the question of the classification of Hamas as a terrorist group," reads the Luxembourg court's ruling.
It also pointed out that Hamas will not gain access to frozen funds which are expected to be blocked for a further three-month period.