The US urged Serbia and Kosovo to immediately de-escalate tensions in northern Kosovo after clashes injured dozens of peacekeepers and protesters, intensifying the international call for calm.

US Secretary of State Antony Blinken blamed Kosovo Prime Minister Albin Kurti’s government for “unnecessarily” inflaming ties with the minority Serb community and urged newly elected, ethnic-Albanian mayors to avoid working in predominantly Serb towns where violence erupted this week. Kosovo police should also withdraw, he said in a statement late Tuesday.

Serbia should call its troops to stand down after President Aleksandar Vucic put them on high alert last week, Blinken said. Vucic should also urge Serbs in Kosovo to “halt challenges to KFOR and refrain from further violence,” he added, in reference to the NATO peacekeeping force.

The statement underscored growing impatience in Washington, which has backed a European Union-brokered negotiation process to resolve a standoff that is blocking both Serbia and Kosovo from making progress toward EU membership.

That process was essentially hamstrung last week when, following an election that Serbs living in northern Kosovo boycotted and declared invalid, ethnic-Albanian mayors tried to access their offices under police escort. Protesters clashed with police, triggering the deployment of NATO-led peacekeeping troops, with 30 soldiers in the KFOR mission and dozens of Serbs hurt in fresh violence on Monday.

The US has decided to exclude Kosovo from the large military exercise Defender Europe 2023. The unusually sharp rebuke is a blow to Kosovo, which depends on the US for financial aid and security, as well as backing in its push for further international recognition of its independence.

That didn’t sit well with Kosovo Prime Minister Kurti, who described Blinken’s rebuke as “unfair, wrong, hurtful and naïve” in a social media post on Wednesday.

The initial trigger for the protests was the municipal election held in April which local Serbs boycotted, with the encouragement of Serbian President Vucic. Kurti pressed ahead with the vote, despite warnings from the US and the EU that it would exacerbate tensions.

The standoff continued on Wednesday. Hundreds of protesters gathered in the morning hours in the Serb-majority towns of Leposaviq and Zvecan, waving Serbian flags. They repeated demands that the newly elected ethnic-Albanian mayors leave their offices and that Kosovo police be withdrawn, former Zvecan official Srdjan Milovic told the Pristina-based Koha news service.

Kurti rejected the demands, saying that as long as “this violent mob outside who is ready to attack” remains, he will keep Kosovo police on site. He added that “if Serb protesters would peacefully ask for a new election,” he would listen.

“What we can do within law and still be doing politics, is at some point early elections,” he said at the GLOBSEC Security conference in Bratislava, Slovakia. “But we cannot say that these mayors are not mayors.”

While the most substantive issue is Serbia’s refusal to recognize the independence of Kosovo, which formalized its break from Belgrade in 2008, the enmity between the two communities dates back to the war in Kosovo a generation ago.

By putting his army on high alert and moving some units nearer to the border on Friday, Vucic’s actions are fueling concerns about just how far the situation in northern Kosovo could deteriorate. Belgrade was forced by NATO to withdraw its forces from Kosovo in 1999.

The flareup comes at a critical moment for the western allies who have backed the Kosovo state since its creation. Russia’s war in Ukraine, meanwhile, means western diplomats have limited bandwidth to focus on another flareup on the European continent.

“I call on all sides to step away from confrontation, and to take measures to restore calm,” European Commission President Ursula von der Leyen said in Bratislava.

Russia and China have both backed Serbia’s position, adding a geopolitical dimension to the dispute, and helping perpetuate the divisions that haunt the countries of the former Yugoslavia.

“China and Serbia are iron-clad friends,” Chinese Foreign Ministry spokeswoman Mao Ning told reporters on Wednesday. China respects Serbia’s efforts to safeguard sovereignty and territory, she said.

--With assistance from Jan Bratanic.

(Updates with Kosovar premier’s comments in 10th paragraph.)