Leaked Document Says Russia’s Ally Serbia Is Sending Arms to Ukraine

A leaked U.S. intelligence document lists Serbia as a country that has sent or is ready to send lethal aid to Ukraine, a revelation likely to create tensions between Russia and the Balkan nation, a close partner for centuries.

The document, dated March 2 and part of a trove of secret intelligence material leaked online, included a chart that put Serbia in a group of European nations that has refused to provide training to Ukraine’s military but has “provided or committed to provide lethal aid.” The existence of the chart, which has been seen by The New York Times, was first reported Wednesday by Reuters.

Unconfirmed reports in Russian news media have said that Serbian weapons and ammunition had found their way into Ukrainian armories, prompting Moscow last month to demand an official explanation and warn President Aleksandar Vucic of Serbia that arming Ukraine was a “serious question” that could damage relations between the two nations.

Serbia on Wednesday denied that it had sent military equipment to Ukraine, as it did in March when pro-Kremlin news media in Russia reported the secretive military aid and Russia’s Foreign Ministry expressed “deepest concern” about the reports.

The bigger question, experts said, is less whether the Serbian weapons have ended up in the hands of Ukraine than whether Mr. Vucic’s government orchestrated their delivery — or, whether it was done without the government’s approval by foreign arms traders working with Serbs inside an armaments industry notorious for corruption and cutting corners.

Serbia has a large weapons industry and produces artillery shells and other items compatible with Ukraine’s mostly Soviet-era weaponry.

Serbia’s defense minister, Milos Vucevic, on Wednesday dismissed the U.S. intelligence document as untrue, saying, “Serbia did not, nor will it be, selling weapons to the Ukrainian or Russian side, nor to countries surrounding that conflict.”

A fellow Slavic nation bound to Russia by a shared Orthodox Christian faith and a long history of close cooperation, Serbia has sought to balance its ties to Moscow with its aspirations to join the European Union.

Serbia declined to join sanctions imposed on Russia by the European bloc, declaring itself neutral in the conflict, but it voted at the United Nations last month for a resolution condemning Russia and demanding it “immediately withdraw” from Ukraine.

Serbia’s application to join the European Union has been stalled for 14 years, but Mr. Vucic, Serbia’s president, has insisted that his country wants to move forward with its request. He has faced strong criticism, however, from hard-line nationalists who want Serbia to draw closer to Russia, not Europe.

Mr. Vucic’s balancing act has been made more difficult by the issue of Kosovo, the former Serbian territory that declared itself an independent state in 2008 but has been bitterly divided between its majority ethnic Albanian population and its small Serb minority, which looks to Russia for protection. Russia, like Serbia and several other European countries with separatist problems, does not recognize Kosovo’s independence, and it has been an important ally for Serbia at the United Nations.

The leaders of Serbia and Kosovo in February verbally accepted a deal mediated by the European Union — and denounced by nationalists in both countries — for the normalization of their relations. It has not been formally signed.