EU leaders have accepted Ukraine and Moldova as candidates to join the bloc, paving the way for accession that is likely to take several years.
European Commission President Ursula von der Leyen tweeted that it was a historic moment and a “good day for Europe”.
“Your countries are part of our European family,” he posted.
Ukrainian President Zelenskyy tweeted: “I sincerely commend the decision of the EU leaders,” saying it demonstrates that “Ukraine’s future lies within the EU.”
Live updates: “Our future is within the EU,” says Zelenskyy
The measure is likely to infuriate Russia, which has opposed the possibility of Ukraine uniting and getting closer to the West.
Ukraine ran less than a week after being invaded in February and its candidacy has accelerated.
European leaders approved the measure at a special summit in Brussels.
Ms von der Leyen said the decision “strengthens Ukraine, Moldova and Georgia, in the face of Russian imperialism. And it strengthens the EU. Because it proves once again to the world that we are united and strong in the face of external threats.”
Moldovan President Maia Sandu has also celebrated a historic moment for her small landlocked nation, which borders Ukraine.
He said there is “a difficult path ahead” but that it offers “more prosperity, more opportunities and more order”. The country is among the poorest in Europe.
Georgia is also on the path to membership
European Council President Charles Michel tweeted that a third country was also taking steps to join the union, the former Soviet state Georgia.
He said the council had recognized “Georgia’s European perspective and is willing to grant candidate status once the outstanding priorities are addressed.”
“Congratulations to the people of Georgia. A historic moment in EU-Georgia relations: Georgia’s future lies within the EU,” he said.
Image: People in Georgia’s capital, Tbilisi, have demonstrated this week in support of EU membership. Image: AP
Candidates must comply with the rules on the state of their economy and the political sphere, including the commitment to the rule of law and other democratic principles.
Ukraine will have to reduce government corruption and enact other reforms.
It is unclear how long the process will take. Turkey, for example, obtained candidate status in 1999, but its application has been blocked by several disputes.
The three countries “have work to do before moving on to the next stage of the process,” Ms. von der Leyen, adding that he knows “they will move quickly.”
If a country joins the EU, it is protected by a treaty clause that requires other members to help if it is attacked.
Ukraine also aspires to join NATO, which is separate from the European Union, but currently this is a remote perspective and President Putin has demanded that he never be allowed to become a member of the military alliance.