Aleksandar Vucic's reaction to Donald Trump's announcement that Belgrade will move its Israeli embassy to Jerusalem next July made some people wonder if the news had come as a surprise to the Serbian leader.

Vucic visited Washington this week to sign a US-brokered deal with Avdullah Hoti, prime minister of the breakaway Serbian region of Kosovo. The agreement was touted as a great diplomatic success for Washington, which managed to bring the two Balkan rivals closer together. Among other things, Kosovo, a Muslim-majority entity, agreed to recognize Israel while Serbia agreed to move its embassy to Jerusalem, following in the footsteps of the US.

The Serbian president's reaction to the announcement, however, made some commenters wonder whether he knew the details of the document that he had signed. As Trump described the pledge as "fantastic," Vucic looked sideways at his American host, then turned pages of the agreement before making a hand gesture, which one could interpret as an aborted face-palm.

Comments online suggested Vucic may not have read the fine print before signing the agreement, and called the scene humiliating. Heads will soon roll among the president's aides, some predicted.

Adding to the confusion, Trump mistakenly called Hoti the "president of Kosovo."