Ambassadors from the EU's 27 member states will meet on Sunday to discuss a solution that could allow them to break the deadlock on the sixth round of economic penalties against Russia, including a historic stop to Russian oil imports, according to EU sources.

The newest set of proposed sanctions has been delayed by landlocked Hungary, which lacks access to maritime oil cargo ships and relies on Russian crude delivered via the Druzhba pipeline for 65% of its oil needs.

Budapest has rejected a proposal to give it two years longer than the rest of the EU to wean itself off Russian oil as insufficient.

It seeks at least four years and 800 million euros ($860 million) in EU money to convert its refineries to process non-Russian petroleum and increase pipeline capacity to neighboring Croatia.

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According to the sources, the compromise approach presented to national negotiators on Sunday consisted of eliminating the Druzhba pipeline from any future oil embargo and only applying sanctions on oil carried to the EU by tanker vessel.

The Druzhba pipeline contributes to one-third of all Russian oil shipments to the EU. The remaining two-thirds are made up of maritime cargo.

France, which now holds the rotating EU presidency, and the European Council, which represents the governments of the EU members, proposed the compromise.

Prevent sixth round of sanctions

Its goal is to break the stalemate that has prevented the EU from implementing the sixth round of sanctions on Moscow over the war in Ukraine since early May.

It plans to stop buying Russian crude oil in six months and Russian petroleum products by the end of the year. It would also impose more penalties on Russian banks and increase the bloc's blacklist of Russian persons.

Postpone sanctions package 

Another possibility under consideration is to postpone the entire package of additional sanctions until a solution to provide Hungary with alternative oil supplies can be discovered, according to the sources.

The quest for a solution has escalated in recent days to avoid differences over Russia clouding the meeting of EU leaders of state and government scheduled for Monday and Tuesday in Brussels.

When the meeting opens on Monday afternoon, Ukrainian President Volodymyr Zelensky will address it via video link, just as he did on different platforms.

If EU ambassadors reach an agreement on an oil embargo on Sunday, it will still need to be ratified by their governments before being presented to the summit.