"If Barzani and the Kurdistan Regional Government do not go back on this mistake as soon as possible, they will go down in history with the shame of having dragged the region into an ethnic and sectarian war", he said.
The Iraqi government and neighboring countries Iran, Turkey, and Syria all strongly opposed Kurdistan even having this referendum, and would be even more livid at an outright declaration of independence.
Neither will the ban apply to military or humanitarian flights, the director of the Kurdistan global airport, Talar Faiq, told a press conference.
Iraqi Prime Minister Haider al Abadi (C) on Wednesday ordered the Kurdish region to hand over control of its airports to federal authorities or face a flight ban. The KRG could lose up to 80 percent of revenue if Turkey decides to halt imports of Iraqi oil via a pipeline that runs through Iraqi Kurdistan.
The Turkish premier, for his part, denounced the Kurdish independence referendum as "a strategic mistake" and said the issue, which has its roots in the excessive demands of some individuals, has undermined tranquility in the region.
Military, humanitarian and diplomatic flights will continue from the airport uninterrupted according to the information relayed from Baghdad, Saleh added.
"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 risky than that, God forbid, and will give way for many regional and worldwide sides to intervene in Iraqi affairs", Sistani said.
"We assure the worldwide community of our willingness to engage in dialogue with Baghdad", he said, insisting the referendum was not meant "to delimit the border [between Kurdistan and Iraq], nor to impose it de facto".
The controversial secession referendum was held on Monday in Iraq's semi-autonomous Kurdistan region in defiance of widespread calls for its cancellation.
Over the past three days, there has been an exodus of foreigners from Kurdistan who fear they won't be able to leave after Friday.
In a statement, EgyptAir also said its flights would halt from Friday "until further notice".
Kurdish officials have repeatedly descried their profits from such sales as central to their fight against the Islamic State group, claiming the money is being used for salaries of the Peshmerga.
Turkey has vast interests in the Kurdish region and needs also its help to combat the Kurdistan Workers' Party (PKK), the Kurdish separatist forces in Turkey, he said.
An Iraqi government order that global airlines halt all flights in and out of the cities of Irbil and Sulaimaniyah will kick in Friday evening local time. Iraq and Turkey have also held joint military drills.
Regional airlines have said they will honor the flight ban.
Defense Secretary Robert Gates arrives at Irbil International Airport in Irbil, Iraq. In response, the Kurdish leadership has been defiant, calling for talks to negotiate the Kurdistan Region's transition into an independent country.