BRUSSELS — European Union leaders struggled Monday to agree to impose an oil embargo on Russia, as Ukraine’s president urged them to set aside their differences and endorse a long-delayed package of sanctions aimed at piling more economic pressure on Moscow to halt the war.

The EU has already imposed five rounds of sanctions on Russia over its war. It’s targeted more than 1,000 people, including Russian President Vladimir Putin and top government officials, as well as pro-Kremlin oligarchs, banks, the coal sector and more.

But a sixth package of measures, announced on May 4, has been held up by concerns over oil supplies. The EU gets about 40 percent of its natural gas and 25 percent of its oil from Russia, and the divisions are embarrassing the 27-nation trading bloc and exposing the limits of its ambitions.

Addressing the EU leaders Monday by video-link in a 10-minute message, Ukrainian President Volodymyr Zelenskyy urged them to end “internal arguments that only prompt Russia to put more and more pressure on the whole of Europe.”

He said the sanctions package must “be agreed on, it needs to be effective, including (on) oil,” so that Moscow “feels the price for what it is doing against Ukraine” and the rest of Europe. Only then, Zelenskyy said, will Russia be forced to “start seeking peace.”

It’s not the first time he has demanded that the EU target Russia’s lucrative energy sector and deprive Moscow of billions of dollars each day in supply payments.

But Hungary is leading a group of EU countries – along with Slovakia, the Czech Republic and Bulgaria – that rely heavily on Russian oil and can’t afford to turn off the pumps. Hungary gets more than 60 percent of its oil from Russia and 85 percent of its natural gas.

Hungarian Prime Minister Viktor Orban was adamant on arriving at the two-day summit in Brussels that a deal was not in sight, while Czech Prime Minister Petr Fiala suggested that delaying oil sanctions against Russia could be a solution.

“We’re ready to get rid of our dependence on Russia’s energy sources … but we’re not able to do it in a short term,” Fiala said.

According to several diplomats, leaders will try to reach a deal for an EU embargo on Russian oil brought in by sea by the end of the year that would cover more than two-third of the EU’s oil imports from Russia.

Orban said he could support the new sanctions if Hungary’s oil supply security is guaranteed. Hungary and Slovakia depend on Russian oil that comes through the Soviet-era Druzhba pipeline.

The problem with hitting sea-transported Russian oil is that countries like Belgium, Germany and the Netherlands – which are most reliant on that form – would suffer a surge in oil prices, distorting competition because Hungary would still be purchasing cheaper Russian oil.

Latvian Prime Minister Krisjanis Karins urged his EU counterparts to get over their differences on oil, saying that member countries are “getting a little bogged down in all of the details and we’re forgetting the big picture.”

“It’s only money, and Ukrainians are paying with their lives,” he said. “Only when Russia is defeated can we in Europe feel safe.”

German Chancellor Olaf Scholz was cautiously optimistic. “Everything that I hear makes it sound as if a consensus could be reached and, sooner or later, it will be,” he told reporters.

European Commission President Ursula Von der Leyen all but ruled out a breakthrough at the summit, saying: “my expectations are low that it will be solved in the next 48 hours.”

If adopted, the new sanctions package would also include an asset freeze and travel ban on individuals. Russia’s biggest bank, Sberbank, would be excluded from SWIFT, the major global system for financial transfers. Three big Russian state-owned broadcasters will also be prevented from distributing their content in the EU.

The two-day summit will also focus on continued EU financial support to Ukraine – probably the endorsement of a $9.7 billion tranche of assistance – and on military help and war crimes investigations.

The issue of food security will be on the table Tuesday, with the leaders set to encourage their governments to speed up work on “solidarity lanes” to help Ukraine export grain and other produce.

Some protesters gathered outside EU buildings Monday before the summit, holding signs like “No to Russian oil and gas.”