PRISTINA, Kosovo — Kosovo’s Parliament overwhelmingly approved legislation on Friday to form an army, prompting criticism from NATO and European Union officials and angering neighboring Serbia, which said it was prepared to use its own army to protect ethnic Serbs in Kosovo.

All 107 lawmakers present in Kosovo’s 120-seat Parliament, which is dominated by ethnic Albanian parties, voted to back the government’s plan to transform the 3,000-strong, lightly armed Kosovo Security Force into an army that would grow to 5,000 active troops and 3,000 reservists in the next decade.

Kosovo Serb lawmakers did not attend the session.

Aleksandar Vucic, Serbia’s president, said in the town of Trstenik in central Serbia on the eve of the vote, “Not a single act in the international law gives them the right to form an army.”

“Everything that Pristina does — and evidently it does it all with support of the U.S. and Britain — is against the law,” Mr. Vucic added.