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Opposition leader Viktor Yushchenko (search) said Thursday that he was sure he was poisoned by the Ukrainian government and believes it most likely happened at a dinner he had with the country's top security service officials.

Yushchenko's comments, made in an interview with The Associated Press, were the first time he pinpointed when and where he believed he was poisoned with dioxin (search). He said it likely happened at a Sept. 5 dinner with the head of the Ukrainian security service, Ihor Smeshko, and his deputy, Volodymyr Satsyuk.

"That was the only place where no one from my team was present and no precautions were taken concerning the food," he said. "It was a project of political murder, prepared by the authorities."

A parliamentary commission that investigated Yushchenko's mysterious illness in October said he had complained of pains — including a headache about three hours after the meal and an acute stomach ache the next day — after meeting with Smeshko. The commission, however, also listed other places he ate or drank that day.

Yushchenko, who was disfigured by poisoning, told The AP that Ukrainian prosecutors were looking into the case and said he was confident the official culprits would be punished.

"I have no doubt that within several days or weeks, this path will lead to the authorities, to specific people representing the government — who administered the poison, who was involved, from whom the poison was procured," he said. "Who blessed it on different levels of government?"

Members of Yushchenko's campaign team had spoken of the security dinner as a possible site of the poisoning, but Yushchenko himself had until now refrained from pointing the finger at specific officials.

Experts say it is impossible for Yushchenko to have naturally acquired such high levels of dioxin. New tests reveal the level in his blood is more than 6,000 times higher than normal and is the second highest ever recorded in human history, said Abraham Brouwer, professor of environmental toxicology at the Free University in Amsterdam, where blood samples taken in Vienna were sent for analysis.

Brouwer's team has narrowed the search from more than 400 dioxins to about 29 and is confident they will identify the poison by week's end.

Poisoning experts say those who spiked Yushchenko's food may have aimed to kill him or may simply have tried to debilitate him during the election campaign.

What constitutes a lethal dose of dioxin has never been established, because nobody has ever been known to die from it.

It's possible that Yushchenko did not eat all of the poisoned meal and so escaped death by accident, but it's also possible that dioxin was chosen because it is recognized as a crippling poison that normally doesn't kill, scientists say.

Speaking on other subjects, Yushchenko criticized Russia's involvement in the Ukrainian campaign as "interference in the internal affairs of Ukraine."

"This is debasing for Russia, it debases its authority, its policies, the entire state. It's not a policy that should be conducted between neighbors," he said.

He said, however, that if he wins the Dec. 26 presidential rerun, he would make efforts to turn a new page in relations with Russia, which heavily backed his rival, Prime Minister Viktor Yanukovych (search).

"Russia is our eternal neighbor, a strategic neighbor," he said. "We must always have excellent relations with it. My government will do everything possible, everything I can, to achieve this."

At the same time, he said Ukraine would move to integrate more closely into European structures and possibly aim at an associate membership in the European Union in three to five years.

He voiced confidence that Ukraine would not split, but reaffirmed the need to punish regional officials in mostly Russian-speaking eastern provinces who had pushed for self-rule as part of their efforts to support Yanukovych.

Early Thursday, Yushchenko warned that "provocations" allegedly being planned by his opponent could jeopardize the Dec. 26 rerun, which the Supreme Court ordered after ruling the Nov. 21 second-round vote fraudulent.

"There is not a 100 percent guarantee that the election will take place," he told reporters at a news conference in the capital. "I know of provocations being prepared in the eastern regions."

Yushchenko did not elaborate on what sort of provocations could be planned.

Yushchenko has been working hard in recent days to expand his base of support from western parts of the country, where Ukrainian nationalism is strong, to the eastern areas, which have strongly backed Yanukovych.

Yushchenko told The AP that allegations he had received campaign financing from the United States were "nonsense."

"Neither I nor my political partners have received or will receive any money from America, from the government or from non-governmental organizations," he said.