Hoshyar Zebari, who helped lead the referendum drive in the Kurdish region and was formerly Iraq’s foreign minister, said that criticism of the vote from the United States had “emboldened Baghdad” to take a hard-line position toward the Kurds. Baghdad’s threatened retaliation was, he said, “very damaging and provocative, and illogical and destructive.”

Mr. Ali said the Kurds were hopeful that international allies would eventually come around to the idea of Kurdish independence, and said they were heartened at some individual voices praising the referendum result. He cited, for instance, Charles E. Schumer of New York, the minority leader in the United States Senate, who on Wednesday praised the Kurdish independence vote.

Iraq’s influential Shia spiritual leader, Ayatollah Ali al-Sistani, in his Friday sermon in the southern city of Karbala, was strongly critical of the Kurdish move. “Any individual steps toward division and separation and the attempt of making this thing reality will lead to internal and external reaction and bad consequences that would damage our dear Kurdish citizens in the first place and maybe lead to what is more dangerous than that, God forbid, and will give way for many regional and international sides to intervene in Iraqi affairs,” Ayatollah Sistani said.

On Friday, military officials in Baghdad confirmed that the strategic highway linking Mosul and the northern city of Dohuk, in Kurdish-held territory, was closed by the Iraqi military for several hours. In addition, protests by civilians forced the closure of the Kirkuk-Baghdad highway on Friday. Saad al-Hadithi, the spokesman for Prime Minister Haider al-Abadi of Iraq, said that land borders would also be closed between Iraq’s Kurdish region and Turkey and Iran, but there was no confirmation if that had happened.

The Iraq border agency announced that it was sending convoys of police officers and Interior Ministry officials to guard three key land border crossings between the Kurdish region and Syria, Turkey and Iran beginning on Saturday.

Mr. Ali said that he was aware of no such move and that it would be unconstitutional.

He said that cutting off the Kurdish region’s trade with Turkey, which he said totals $17 billion a year, would hurt everyone.