In video posted to Facebook on Wednesday, Hungarian Foreign Minister Peter Szijjarto warned that Hungary will prevent Bulgaria’s entry into the EU’s passport-free Schengen travel area unless Bulgaria eliminates its new transit tax on Russian gas. Szijjarto said that if necessary, Hungary will exercise its veto power in the European Council.

Szijjarto said, “We have made it clear to the Bulgarians that if they keep this in place for long, if they jeopardize the safety of Hungary’s energy supply for long, then we will veto their Schengen entry.” He went on to call Bulgaria’s tax “scandalous and hostile,” and “completely contrary to European legislation,” noting that it threatened to cease crucial Russian gas flows to Hungary and other nations of the EU which require the delivery of Russian gas which travels through Bulgaria.

In October, Bulgaria imposed an additional tax of 20 Bulgarian lev ($10.76) per megawatt-hour on Russian natural gas which entered Bulgarian territory. Hungary, claiming the new tax threatened its energy security due to its reliance on Russia for most of its gas supplies, called the new tax “unacceptable.” Ever since then, Budapest has been pressuring Bulgaria to lift the tax.

According to reports in the media, officials from Hungary and Bulgaria had held meetings in the past week to discuss the tax, and a preliminary agreement was already reached. Szijjarto said in his Facebook post that the critical decision on Bulgaria’s entrance into the Schengen zone would be made next week, and “that’s why they suddenly started trying hard to eliminate this tariff.”

The foreign minister concluded, “If they do, we will also reverse our decision on the veto.”