European Commission President Ursula von der Leyen delivered pointed remarks Wednesday to Serbian President Aleksandar Vučić about his country’s progress toward EU membership.

“Now is the moment for Serbia to get concrete about joining our union,” said the Commission chief, during a press conference in Belgrade on her tour of the Western Balkans.

“Therefore, we need to see progress, on the rule of law, the electoral framework and media freedom,” von der Leyen added.

“I know these reforms are not easy,” she said. “They take patience and endurance. They must include all parts of society and the political spectrum. But they are worth the effort. Because they move you closer to your goal.”

Von der Leyen also urged the Serbian president to join the EU in imposing sanctions against Russia. Belgrade has consistently refused to align with the bloc in sanctioning Russian energy and goods, especially since it is almost entirely dependent on Russian gas.

“I commend you for reaching 61 percent of alignment with our foreign policy. But more is needed. We want to count on Serbia as a reliable partner,” said von der Leyen.

Serbia applied for EU membership in 2009 and was subsequently granted candidate status in 2012, later opening accession negotiations with the EU in 2013. Since then, 22 of the 35 chapters of accession criteria have been opened — but only two have been provisionally closed.

Leadership in the Western Balkan country has come under heavy criticism in recent years. Protests triggered by the collapse of the Novi Sad train station canopy in November last year turned into a wider revolt over corruption, accountability, and democratic backsliding, which was met with a violent response from police.

The European Green Party criticized the Commission chief’s visit to Serbia, calling it “deeply regrettable that von der Leyen honors Vučić with an official visit without visible reservations, while his regime unlawfully detains students and opposition members and violently represses protesters,” its co-chair Vula Tsetsi said in a statement.

The U.S. decided last week to sanction Serbia’s leading oil supplier, the Petroleum Industry of Serbia (NIS), because it is majority-owned by Russia’s Gazprom Neft.

Vučić met with Russian President Vladimir Putin in Beijing during a regional security summit in September, reaffirming Serbia’s commitment to purchasing Russian gas and potentially increasing it.

“Since the beginning of the Ukrainian crisis, Serbia has been in a very difficult situation and under great pressure, but … we will preserve our neutrality,” said Vučić, utilizing Kremlin terminology for its war on Kyiv.