Iraq's foreign minister has warned of serious consequences if Turkey launches a ground assault against Kurdish rebels based in northern Iraq.
Hoshyar Zebari told the BBC that the current crisis was "dead serious" and accused Turkey of not seeking a peaceful solution.
He said Turkey had shown no interest in Iraqi proposals to calm the situation.
Turkey has 100,000 troops near the border and is threatening to attack the Kurdistan Workers' Party (PKK) in Iraq.
The group frequently launches deadly attacks on Turkish troops, and is accused by Ankara of using the Kurdish semi-autonomous area of northern Iraq as a safe haven.
Mr Zebari said Turkey demanded that Iraq hand over senior members of the PKK sheltering in Iraq, a request he said was impossible to fulfil.
"They are not under our control, in fact. They are up in the mountains, they are armed," he said.
He said there was nothing to stop Turkey taking action against PKK bases in the remote and rugged border mountains.
Formed in late 1970s
Launched armed struggle in 1984
Dropped independence demands in 1990s
Wants greater autonomy for Turkey's Kurds
Leader Abdullah Ocalan arrested in 1999
Ended five-year ceasefire in 2004
Called a terrorist organisation by Turkey, the EU and US
But the massing of an estimated 100,000 Turkish troops - with tanks and other heavy weaponry - raised fears that the Turks were planning something bigger and deeper into northern Iraq, Mr Zebari said.
Such a step would have "disastrous consequences" for stability in both countries and in the wider region, he added.
"This would be a unilateral decision and that's why people are resisting that.
"That's why the whole government of Iraq and the whole people of Iraq are united really not to see their sovereignty, their territorial integrity undermined by a friendly neighbouring country."
The BBC's Jim Muir, in Baghdad, says there are fears of a collision between Turkish troops and the Iraqi Kurdish forces which control the area.
The Kurdish north of Iraq is a semi-autonomous area run by the Kurdish Regional Government, led by Masoud Barzani.
Speaking to al-Jazeera TV, Mr Barzani insisted he would not hand over anyone to Turkey, but added that he would also not allow the area to be used as a base for a rebel group.