Baghdad rejects the KRG's move to press for independence as Germany and US also express concern.
Turkey on Friday warned that a decision by Iraq's autonomous Kurdish region to hold an independence referendum would be a "grave mistake."
Turkey was responding to an announcement on Wednesday by Kurdish Regional Government (KRG) President Massoud Barzani that the KRG would hold a referendum on September 25 to gauge support for independence of the KRG-governed region in Iraq.
The expected 'yes' vote would strengthen the KRG's hand in talks with Baghdad on the possibility of splitting off the KRG-governed area from the rest of Iraq to form an independent region.
Turkish Prime Minister Binali Yildirim on Friday said the call for a referendum was an "irresponsible" decision that would add to the region's problems.
Speaking to reporters on Friday, Yildirim reiterated Turkey's support for Iraq's territorial integrity. He added, "There are sufficient problem areas in our region and we don't think it is right to create new problem areas."
Earlier, the Turkish foreign ministry released a statement on the issue: "We believe that the announcement by the [Iraqi Kurdish region] to hold an independence referendum on September 25 ... will constitute a grave mistake... The maintenance of Iraq's territorial integrity and political unit is one of the fundamental principles of Turkey's Iraq policy."
Ankara said the major issue faced by Iraq was the fight against Daesh and to rebuild the country after the offensive, which appears to be reaching a conclusion.
Turkey's foreign ministry said the solidarity shown in the fight against Daesh "should be pursued in the post-Daesh period and the issues that concern the future of the country should be tackled with international and constitutional legitimacy."
"It is clear that under those extraordinary conditions, a referendum on regions whose status are disputed will be far from reflecting the people's will," the foreign ministry added.
Iraq, Turkey, Iran and Syria have all historically opposed an independent Kurdish-majority region.
Baghdad rejects unilateral move for independence
The Iraqi government would reject any move by Kurdish regional authorities to press unilaterally for independence, a government spokesman said on Friday in Baghdad.
"No party can on its own decide the fate of Iraq, in isolation from the other parties," spokesman Saad al Haddithi said in a statement.
"Iraq is constitutionally a democratic, federal country with full sovereignty ... Any measure from any side in Iraq should be based on the constitution,'' Haddithi said.
US concerned Iraqi Kurdish referendum will distract from war
The US State Department said on Thursday it was concerned that a non-binding independence referendum planned this year in Iraq's autonomous Kurdish region will distract from "more urgent priorities" such as the defeat of Daesh.
While saying it appreciated the "legitimate aspirations" of the Kurds in northern Iraq, the State Department said in a statement it supports a "unified, federal, stable and democratic Iraq" and had voiced concerns about the planned September referendum to Kurdish authorities.
"We ... encourage the regional authorities to engage with the government of Iraq on the full range of important issues, including the future of relations between Baghdad and Erbil, on the basis of the Iraqi constitution," the department said.
Germany warns Iraqi Kurds against "one-sided" referendum plans
Germany said on Thursday it was concerned plans by Iraq's autonomous Kurdish region to vote on independence in September, could exacerbate tensions in Iraq.
"We can only warn against one-sided steps on this issue. The unity of Iraq is on the line," Foreign Minister Sigmar Gabriel said in a statement. "Redrawing the lines of the state is not the right way and could exacerbate an already difficult and unstable situation, in Erbil as well as Baghdad."
Germany is a major partner of the Iraqi Kurds. It has provided 32,000 assault rifles and machine guns, as well as other weapons valued at around 90 million euros since September 2014.
About 130 German soldiers are based in Erbil where they are providing training to the Kurdish peshmerga fighters.
"I call on all sides to seek dialogue, to find consensus for dealing with open questions, and not to reignite conflicts in the disputed areas of Erbil and Baghdad," Gabriel said.
He said it was imperative to maintain unity within Iraq to enable the continued fight against Daesh, that has seized territory in Syria and Iraq.
"The fight against Islamic State [Daesh] has not yet been won. Only together will it be possible to take the next and perhaps most important steps to deal with the challenges to come," he said.
A senior Kurdish official, Hoshiyar Zebari, had said in April the expected "yes" vote would strengthen the Kurds' hand in talks on self-determination with Baghdad and would not mean automatically declaring independence.