The trial of acclaimed Turkish novelist Orhan Pamuk casts a shadow over the country's entry talks to the EU, a senior EU official has warned.
Orhan Pamuk is modern Turkey's best-known novelist
Olli Rehn, who oversees Turkey's moves to join the EU, described the trial as a litmus test as to whether Turkey was committed to freedom of expression.
The writer has been charged with denigrating Turkish national identity.
He faces trial for remarks about Turkey's killing of Armenians during World War I and Kurds in the 1980s.
Ankara denies the deaths can be classed as a genocide and accuses Mr Pamuk of "insulting Turkishness".
The charges relate to a magazine interview earlier this year in which Orhan Pamuk said: "One million Armenians and 30,000 Kurds were killed in these lands and nobody but me dares talk about it."
He could face up to three years in jail if convicted.
Mr Rehn said the "trial of a novelist who expressed a non-violent opinion casts a shadow" over negotiations for Turkey's entry into the EU.
He added that it presents an "opportunity to set a positive precedent for the numerous other cases of free speech that are awaiting trial".
"It is not Orhan Pamuk who will stand trial tomorrow, but Turkey," Mr Rehn said.
The EU officially inaugurated talks on Turkey's entry into the bloc in October this year.
Days later, Mr Rehn visited Mr Pamuk in Istanbul, bought several of his books and declared he was a fan of the writer, the Associated Press news agency reports.
Human rights groups have urged the EU to ensure Turkey's laws on freedom of speech match those in western Europe before it admits the country into the bloc.
Mr Pamuk is a passionate advocate of admitting Turkey into the EU.
His books, including My Name is Red and Snow, have been internationally acclaimed for dissecting Turkey's vibrant, often strained, ties to Europe and Asia.