The delay also comes shortly after voters in the Netherlands rejected an association agreement between the European Union and the former Soviet republic, which has caused tensions with Russia.
"The presidents of the European Council, European Commission and Ukraine have jointly agreed to reschedule the bilateral EU-Ukraine Summit planned for 19 May until September," a European Commission spokeswoman said.
"In the meantime, the new Ukrainian government will pursue work on delivering its reform commitments" under the association deal, the spokeswoman added.
"The rescheduling of the summit should also allow for the review of the IMF programme to be concluded, and for a further assessment of the provisional application of the Association Agreement" including a trade deal, she said.
The 28-nation EU 's association agreement with Ukraine has been at the heart of the crisis in the country since the 2014 toppling of Moscow-backed president Viktor Yanukovych, who had rejected the deal.
Russia annexed the territory of Crimea shortly afterwards and the EU imposed sweeping economic sanctions against Moscow, while pursuing the deal with the new government in Kiev.
But there has been growing unease in Brussels at the slow pace of reforms in Kiev and the increasingly volatile political situation following the resignation of embattled Prime Minister Arseniy Yatsenyuk.