The twelve new names, due to be published Friday, include some "really high-ranking" individuals, said Van Rompuy.
The bloc also cancelled a planned June 3 summit with Russia.
Also, the European Commission President Jose Manuel Barroso said that the EU would provide EUR 1.6 billion financial aid to Ukraine and open its market to Ukrainian goods.
The EU will also help Ukraine implement reforms and secure its independence, added Barroso.
Ukraine's interim Prime Minister Arseniy Yatsenyuk is to sign the political chapters of the association agreement with the EU, Van Rompuy and Barroso said.
