Serbian President Aleksandar Vucic said he will “take all measures to protect” ethnic Serbians and put his nation’s army at its “highest level of combat readiness” as tensions flared Tuesday with Kosovo, the BBC and Daily Beast report.

In 2008, Kosovo won independence from Serbia, though Belgrade “still considers Kosovo to be an integral part of its territory and rejects suggestions it is whipping up tensions and conflict within its neighbor’s borders,” Reuters explains. The current standoff stems from a dispute over license plates; Kosovo wants the 50,000 Serbs living in its north to switch from Serbian plates to ones issued by Pristina. Serbs in the ethnically divided Kosovar city of Mitrovica erected roadblocks on Tuesday in protest, prompting Vucic’s threats against Pristina if the government retaliates.

Kosovo called on NATO peacekeepers, some 3,700 of whom are staged in the country, to remove the roadblocks. Threatened by a second war on the continent, the European Union called for “maximum restraint and immediate action” to resolve tensions, but “any kind of inadvertent spark could really set this off at this point,” the Atlantic Council’s Damir Marusic told Semafor.