By Christian Fraser
BBC News, Rome
Italy has cancelled an official visit to Croatia following an angry exchange over the massacre of thousands of Italians during World War II.
President Napolitano described the massacre as "ethnic cleansing"
In 1943-45, up to 10,000 were tortured or killed by Yugoslav communists who occupied the Istrian peninsula, now part of Croatia and Slovenia.
On Saturday, Italian President Giorgio Napolitano, an ex-communist, described the murders as "ethnic cleansing".
Croatian leader Stipe Mesic said his speech had traces of "open racism".
This little known chapter of World War II still causes Italians great pain and division.
It is known as the Foibe, after the deep mountain chasms into which the victims were thrown.
At the end of the war, it was largely hushed up by the politicians, who were keen to heal Italy's war wounds and move on with reconstruction.
It also sat uncomfortably with the image communist partisans had forged as national heroes, who had saved the country from an alliance with Adolf Hitler.
'Wave of hatred'Last weekend, at only the third remembrance day held for Foibe victims, President Napolitano said the massacre had been motivated by "a wave of bloodthirsty hatred and fury as well as a Slavic annexation plan".
It was a speech which offended his Croatian counterpart Stipe Mesic, who wrote saying "it was impossible to not see overt elements of racism, historical revisionism and a desire for political revenge".
The letter has sparked an unusual war of words.
Foreign Minister Massimo D'Alema on Tuesday cancelled a trip to Zagreb and summoned the Croatian ambassador.
Italian Prime Minister Romano Prodi contacted the Croatian prime minister "to express his contempt for the unjustifiable words that, among other things, comes after a period of great collaboration".
Italy wants talks on Croatian EU membership to include compensation for property that Italians lost in Istria and Dalmatia during World War II - something the Croatians seem open to discuss.
But a spokesman for the Croatian prime minister suggested it was time for the two sides to open a mutual commission to investigate properly those crimes committed during and after World War II.