European Council President Donald Tusk | Philippe Huguen/AFP via Getty Images Donald Tusk to Ukraine: Europe has got your back Council president, in Kiev, says EU doesn’t see any ‘symmetry’ in responsibility for conflict with Russia.

European Council President Donald Tusk reassured senior Ukrainian leaders Thursday of Europe's support in the country's continuing conflict with Russia.

EU leaders have long sought to play a role as moderator in the conflict in eastern Ukraine, including helping to broker the Minsk 2 peace agreement that so far has not been fulfilled.

But during a visit to Kiev, the Ukrainian capital, Tusk met with President Petro Poroshenko and Prime Minister Volodymyr Groysman and told them the EU did not regard Russia and Ukraine as equally responsible for the ongoing strife.

"We will continue our discussion in Europe about how to help Ukraine implement the Minsk agreement, how to achieve a real ceasefire, and then I hope peace," Tusk said, sitting across from Groysman at a morning meeting. "It's also my role in Europe to explain every day that there is no symmetry between Russia and Ukraine when it comes to the Minsk implementation process, that one side is the aggressor, the second one is the victim. There is no political equilibrium and what I want to confirm today is our support in this really difficult process."

Some EU leaders have grown frustrated at the slow pace of reforms in Ukraine, including faltering efforts to combat corruption.

Tusk's visit to Ukraine comes as EU leaders face mounting economic and political pressure to end economic sanctions against Russia that were imposed after Russia's annexation of Crimea in March 2014, and the Russian-backed separatist violence in the eastern region of Donbas that began later that spring and has now dragged on for more than two years.

EU leaders have already agreed to discuss the bloc's overall relationship with Russia at a summit in Brussels next month.

At a separate meeting, Poroshenko urged Tusk to maintain pressure on Russia. “We count on preservation of solidarity with Ukraine and continuation of sanction pressure on Russia until full restoration of sovereignty and territorial integrity of Ukraine," he said.

Leaders in some EU countries have grown frustrated at the slow pace of reforms in Ukraine, including faltering efforts to combat corruption.

Analysts say European leaders face an ever deepening challenge in Ukraine. In a new research paper, Balázs Jarábik and Mikhail Minakov of the Carnegie Endowment for International Peace, noted that Poroshenko has consolidated power among a close circle of loyalists even as reforms have stumbled and the conflict in the east is at stalemate.

"The window for radical reforms appears to be closing," Jarábik and Minakov warned, adding, "As the Ukraine crisis loses salience with Western policymakers, the challenge will be maintaining pressure on leaders in Kiev to deliver meaningful reforms that benefit people’s lives while also convincing the Kremlin to engage seriously in the search for a diplomatic solution amid a continued impasse over implementation of the Minsk accords."

But on a visit to Brussels this week, the Ukrainian justice minister, Pavlo Petrenko, asserted that Ukraine's government had made remarkable progress considering the wartime circumstances, in which officials are struggling to overhaul many of the country's government institutions, its constitution and its economy.

"We have to change everything," Petrenko told POLITICO, adding that he had faced skeptics in the European Parliament who demanded to know why the changes weren't happening more quickly.

The EU is financing some of the reforms, including Petrenko's effort to revamp the judicial system.

"I ask them only one question," Petrenko said. "Give me an example of any country in the European Union who during war made such changes, such reforms, which are not popular."

The EU is financing some of the reforms, including Petrenko's effort to revamp the judicial system. On Monday, a European Parliament committee voted to approve a plan for visa-free travel for Ukrainians, but it is unclear how soon such a visa liberalization regime might be implemented given the complex politics of the issue.

In Kiev, Tusk also attended a commemoration of the 75th anniversary of the massacre of more than 33,000 Jews at Babi Yar, during the Nazi occupation.

Groysman, who is Jewish, praised Tusk for his support of Ukraine both as president of the European Council and as a former prime minister of neighboring Poland. "If someone asks me what should the true friend of Ukraine look like, I would say that the epitome of the true friend of Ukraine is President Tusk," he said.