The Lukoil oil transit dispute is an ongoing international relations dispute between Ukraine and the European Union at odds with Hungary and Slovakia regarding the allowance of the pipeline transfer of Russian oil through Ukrainian territory. The diplomatic standoff arose when Ukraine imposed sanctions[when?] on Lukoil — Russia's largest private oil firm — effectively halting oil supplies to Hungary and Slovakia via the Druzhba pipeline, which the latter two nations stated would lead to an energy crisis and economic collapse. In response, Hungary and Slovakia complained to the European Commission while threatening to halt military aid shipments, energy, and diesel supplies to Ukraine.[1]