By Matthias Williams and Pavel Polityuk
KIEV (Reuters) - European Commission chief Jean-Claude Juncker said corruption was undermining all efforts to rebuild Ukraine in line with European Union norms, as President Petro Poroshenko vowed on Thursday to pursue ever-closer integration with the bloc.
Juncker and European Council President Donald Tusk were in Kiev for a 24-hour summit with Poroshenko following the final ratification of a new trade pact that has angered Russia.
"What we are asking .. is to increase the fight against corruption, because corruption is undermining all the efforts this great nation is undertaking," Juncker said at a joint briefing.
"We remain very concerned," he said.
The criticism suggests the EU delegation may have taken a tougher-than-expected line in talks forecast to be largely upbeat after the confirmation on Tuesday of an association agreement for closer political and trade ties.
The pro-Western government in Kiev has sought to boost EU relations since the ouster of a Moscow-backed president in 2014, implementing reforms in exchange for billions of dollars in aid and a new visa-free travel deal with the European Union.
But Ukraine's allies have repeatedly expressed concern that vested interests and corrupt practices remain entrenched, partly due to weak rule of law.
The European Union and the Ukraine's main financial backer, the International Monetary Fund, have called for the creation of a specialized anti-corruption court, but Juncker said a new solution had been agreed at the summit.
"Today we agreed that if Ukraine establishes ... a special chamber devoted to this issue, that will be enough," he said.
Mykhailo Zhernakov, a judicial expert at the non-governmental coalition Reanimation Package of Reforms, said the agreement would be a big disappointment to those campaigning for greater accountability in the justice system.
"There's no way that a chamber in any court will be as independent as a separate court," he told Reuters. "It's not going to help."
While full EU membership for Ukraine remains far off, Poroshenko stressed that Kiev hopes to integrate further by joining the customs union and becoming a member of the bloc's Schengen open-border zone.
"As early as today, it's important to start developing a roadmap to the realization of our dreams," he said at the briefing.
(Writing by Alessandra Prentice; Editing by Catherine Evans)