The United States on Friday urged Kosovo to postpone demands that the Serb minority switch to government plates, accusing the Western-backed state of being uncompromising.

The European Union negotiated an agreement in August to allow free movement between Kosovo and Serbia in a bid to defuse tensions following a series of violent incidents.

Kosovo has given all residents a deadline of the end of the month to switch to their number plates, a move opposed by much of the Serbian minority, who insist on keeping the plates from Belgrade as they share the majority Albanian Kosovo 2008 declaration not accepting independence.

The United States, which with its NATO allies supported Kosovan forces when they fought Serbia in 1999, said Kosovo was within its rights but should postpone the rule to allow time for EU-led diplomacy between the two sides admit.

“The United States is disappointed and concerned that the Kosovo government has rejected requests from its international partners,” said State Department spokesman Ned Price.

“Kosovo and Serbia should work urgently and flexibly to reach a comprehensive agreement on normalized relations that focuses on mutual recognition.”

Under the Brussels Agreement, Serbia has agreed to abolish an entry/exit document for Kosovar ID card holders, and Kosovo has agreed not to introduce one for Serbian ID card holders.

Serbia has been a candidate to join the European Union since 2012, but its prospects are viewed as bleak without a normalization of relations with Kosovo.

Tensions have been exacerbated by the war in Ukraine, as many Serbs sympathize with traditional ally Russia.