Zelensky was visiting Brussels, days after the EU said it was opening formal membership negotiations with Kyiv, where he will meet some of Ukraine's staunchest supporters in the face of the Russian invasion.

"We will sign three security agreements, including one with the EU as a whole," Zelensky said in a post on X.

"For the first time, this agreement will enshrine the commitment of all 27 Member States to provide Ukraine with extensive support, regardless of any internal institutional changes," he said.

Ukraine has signed 17 similar bilateral security agreements, including with the United States, France, Germany, Britain and Japan.

They are not mutual defence pacts, but instead outline key countries' commitments to support Ukraine with military, financial, humanitarian and political aid over a number of years.

"Each step we take brings us closer to our historic goal of peace and prosperity in our common European home," Zelensky said.