BELGRADE — Vice President Joe Biden on Tuesday offered condolences to the families of those killed during the Balkan wars, including the victims of the NATO air war against Serbia.

As a senator, Biden was a strong advocate of the NATO bombing of Serbia in the 1990s. He once said that his work to end the Yugoslav wars was one of the ‘‘proudest moments’’ of his long political career.

The US-led bombardment in 1999 stopped Serbia’s crackdown against ethnic Albanian separatists, ending Belgrade’s rule over its former province of Kosovo. The intervention, when thousands were killed, shifted many Serbs from their generally pro-Western views to their traditional ally Russia.

‘‘The memories of the loss of the loved ones are still fresh,’’ Biden said after his talks with Serbian Prime Minister Aleksandar Vucic.