A photo taken on May 5, 2022 shows the receiver station of the Druzhba pipeline of petroleum between Hungary and Russia at the Duna (Danube) Refinery of Hungarian MOL Company located near the town of Szazhalombatta, about 30 km south of Budapest. AFP
The package suggested last week by the European Commission would have seen most EU members halting oil imports from Russia by the end of the year, to punish Moscow for invading Ukraine.
But several member states, most vocally Hungary, demanded exemptions from the ban and or support to help them escape their long-standing dependence on a single pipeline for Russian crude.
Prime Minister Viktor Orban has declared the package as presented crossed a "red line" for Hungary, but diplomats in Brussels insist the technical negotiations are not blocked.
Ambassadors were to meet again on Sunday, but hopes that the package will be ready before Monday -- to send a signal to Moscow on Russia's Victory Day celebrations -- were fading.
EU foreign policy chief Josep Borrell has said that if there is no agreement over the weekend he will call a meeting of foreign ministers next week.
Any decision on sanctions would have to be approved unanimously by member state governments.
"There is no political blockage, but the need to guarantee alternative sources of supply to landlocked countries dependent on Russian oil by pipeline. And it is not easy," a European diplomat told AFP.
"These are new infrastructure and technological changes, which require not only European funding, but agreements between several member states. We are making progress, but that automatically takes time."
Hungary, Slovakia and the Czech Republic have been offered permission to continue importing Russian oil until the end of 2024, but they also want help securing new sources of oil and retooling their refineries.