Syria has denounced international envoy Lakhdar Brahimi as "flagrantly biased", casting doubt on how long the United Nations-Arab League mediator can pursue his peace mission.
The Syrian Foreign Ministry was responding to remarks by Mr Brahimi a day earlier.
Mr Brahimi ruled out a role for President Bashar al-Assad in a transitional government and effectively called for the Baathist leader to quit.
He told the BBC, referring to Mr Assad: "In Syria...what people are saying is that a family ruling for 40 years is a little bit too long,"
"President Assad could take the lead in responding to the aspiration of his people rather than resisting it," the veteran Algerian diplomat said, hinting the Syrian leader should go.
The Foreign Ministry in Damascus said it was very surprised at Mr Brahimi's comments, which showed "he is flagrantly biased for those who are conspiring against Syria and its people".
The ministry later said it was nevertheless still willing to work with the envoy to find a political solution to the crisis.
Mr Brahimi has had no more success than his predecessor Kofi Annan in his quest to resolve the 21-month-old conflict in which more than 60,000 people have been killed.
Russian and US diplomats, who back opposing sides of the war, will meet Brahimi in Geneva tomorrow.
Ahead of the meeting, Russia repeated its insistence that President Assad must not be pushed from power by external forces and that his exit must not be a precondition for negotiations.
Syria's al-Watan newspaper said Mr Brahimi had removed his "mask of impartiality" to reveal his true face as a "a tool for the implementation of the policy of some Western countries".
Last Sunday President Assad, made his first public speech in six months.
He offered no concessions and said he would never talk to foes he branded terrorists and Western puppets.
Foreign ministers call for Syria to be referred to the ICC
In a joint letter with the foreign ministers of Austria, Slovenia and Denmark, Tánaiste Eamon Gilmore has called for Syria to be referred to the International Criminal Court.
In the letter, the ministers say they have been following the events in Syria "with growing concern".
The ministers say they are particularly worried about a recent attack on UN peacekeepers and reports suggesting the potential use of chemical weapons in the country.
"The al-Assad regime is preparing Damascus for confrontation with the rebels and we know that these situations of last stand urban fighting often result in the most terrible atrocities being committed in armed conflict, with particular dangers for civilians."