WASHINGTON, United States - The United States on Monday condemned a deadly clash between authorities in Kosovo and gunmen near the Serbian border which left one officer dead.

Secretary of State Antony Blinken called on Kosovo and Serbia to avoid any actions or language that could further inflame the situation after Sunday's violence.

"The perpetrators of this crime must be held accountable via a transparent investigative process," Blinken said in a statement.

The clash followed followed months of mounting tensions between the government in Pristina and Serbia.

Two decades after a war between ethnic-Albanian rebels and Serbian forces, Serbia still does not recognize its former province's independence.

Kosovo remains overwhelmingly populated by ethnic-Albanians, but in the northern stretches of the territory near the border with Serbia, ethnic-Serbs remain the majority in several municipalities.

The attack came more than a week after negotiations between the leaders of Serbia and Kosovo failed to make a breakthrough during EU-mediated negotiations in Brussels.

"We call on the governments of Kosovo and Serbia to refrain from any actions or rhetoric which could further inflame tensions and to immediately work in coordination with international partners to de-escalate the situation, ensure security and rule of law, and return to the EU-facilitated dialogue," Blinken said.