KIEV, Ukraine – Ukrainian President Viktor Yushchenko said Thursday he believes a former ally and friend was involved in his near fatal poisoning four years ago.

Yushchenko at a news conference named David Zhvania, a member of a pro-presidential parliamentary faction and the godfather of one of his children, in a sharp departure from the past when he has refused to identify who he thought was responsible.

Yushchenko fell gravely ill after attending a dinner with Zhvania and hosted by two top security officials. Doctors later diagnosed his illness as severe dioxin poisoning that disfigured his face.

Yushchenko has consistently said he knew who was responsible for the poisoning but did not want to name them while an investigation continued.

But Zhvania has angered Yushchenko by claiming earlier this summer that the president suffered only from food poisoning and his staff invented a politically motivated attack to boost his popularity during a closely fought 2004 presidential campaign.

Asked Thursday at a news conference whether he thought Zhvania took part in the poisoning, Yushchenko answered: “I think yes, to put it mildly.”

He gave no evidence for his claim. Zhvania could not immediately be reached for comment.

Prosecutors said Wednesday they had failed to find any suspects. But after being questioned by prosecutors earlier this week, Yushchenko hinted the investigation would produce some “very unpleasant” surprises.

The president has accused Moscow of stalling the investigation by refusing to extradite key figures in the case and provide Russian-made dioxin for testing.

Many here point the finger at the Kremlin, because Yushchenko was running against a Kremlin-backed candidate and because Russia is one of the few countries that produces the dioxin of the formula found in Yushchenko's body.

Zhvania fell out with Yushchenko shortly after he became president following a wave of mass protests in 2004 known as the Orange Revolution. Zhvania has said he disagreed with the president's policies.

The dispute has led Yushchenko's office to seek to strip Zhvania, an ethnic Georgian, of his Ukrainian citizenship. Zhvania's party said in a statement Thursday that the actions were illegal and that he is suing Ukrainian authorities in the European Court of Human Rights.