Turkey was warned by the European Commission on Monday that sending its troops into Iraq could "complicate" its EU membership chances.
Turkey is facing universal pressure to keep troops at home
Individual EU nations also warned against the plan to deploy soldiers in Kurdish-controlled areas, as did the US, whose envoy Zalmay Khalilzad said another round of talks with Turkish officials had ended without agreement.
But Turkish Justice Minister Cemil Cicek indicated that the deployment would go ahead in the face of world disapproval, echoing statements on Sunday by Prime Minister Recep Tayyip Erdogan.
A European Commission spokesman said the move would "bring extra complications" to Turkey's EU membership bid.
"Any action by a neighbour (of Iraq) that could destabilise the situation would be most unwelcome," Jean-Christophe Filori told reporters.
The current and future presence of Turkish troops in Iraq is the result of humanitarian considerations and concerns about
Turkish Justice Minister Cemil Cicek
European Commission President Romano Prodi said a Turkish incursion into Iraq would be "a very serious act" which would "contradict a whole series of undertakings by the Turkish Government."
Mr Cicek said Turkey would make its own decisions.
"The current and future presence of Turkish troops in Iraq is the result of humanitarian considerations and concerns about
terrorism," he said.
He added that Ankara and Washington agreed in principle to a Turkish military intervention in northern Iraq.
It would be entirely unacceptable for there to be any incursion
UK Prime Minister Tony Blair
US diplomats, however, said there was no deal.
"We taked about the Turkish desire to have a presence in northern Iraq. We do not have an agreement on this issue yet," said Mr Khalilzad, Washington's envoy to the Iraqi opposition.
UK Prime Minister Tony Blair joined the wave of pressure on Turkey.
>"It would be entirely unacceptable for there to be any incursion," he said in the UK parliament.
German Defence Minister Peter Struck added his own warning, threatening to withdraw German AWACS crews from Nato's current mission to protect Turkey.
"There should be no reinforcement of the Turkish military presence above its current level," Mr Struck.
A similar warning was issued on Sunday by Belgian Foreign Minister Louis Michel.
"Very strong pressure must be put on Turkey to let it know that taking such action will be a
determining factor in refusing it entry to Europe," Mr Michel said.
After years of battling for a date to embark on EU membership talks, Turkey was assured last year that they would start in December 2004 or soon afterwards, if Ankara had met certain conditions in the meantime.
But opposition has remained strong in some quarters to the idea of a Muslim nation, with most of its territory technically in Asia, joining what is so far a Western European Christian club.
The European warnings come after weeks of steadily growing friction betwen Turkey and the US.
Alone in the world
Washington wanted to launch a land invasion from Turkey, but emerged with only overflight rights after months of wrangling.
US President George W Bush said on Sunday that the US was making it "very clear" to the Turks that they should not cross the border.
Turkish newspaper Sabah said on Monday that Turkey had been left all alone in the world - with Washington, Brussels and Baghdad all angered by its decisions.
The situation in northern Iraq become more unclear on Monday amid Kurdish claims that a second US front was being prepared there.
A US officer has confirmed the presence of American troops in Kurdish areas, but did not say whether a second front was being planned.
On Saturday night four planes landed at an airfield near Sulamaniyah, carrying scores of US special forces, said a senior official from the Kurdish PUK party.