Kiev, Ukraine ? President Viktor Yushchenko said Thursday that investigators were closing in on those who poisoned him with a massive dose of the industrial pollutant dioxin during last fall’s campaign, and that the suspects served in the highest circles of the government of his predecessor, Leonid Kuchma.

“The circle of suspects is narrowing. Prosecutors are now receiving information about the poison itself, its chemical features, and the way of its possible application,” Yushchenko said at the House of Chimeras, a 19th century building decorated with statues of mythical creatures that is used for official functions.

“When it comes to who did it — it was the regime itself. The people in power. No doubt about that,” he said. He did not give names, but he has repeatedly noted that he became ill after eating dinner with senior officials of the national security service in September, as his campaign to succeed Kuchma was accelerating.

Yushchenko, a pro-Western reformist, defeated Kremlin-backed Viktor Yanukovych in last year’s bitterly contested election. Kuchma had hand-picked Yanukovych as his intended successor.

The poisoning left Yushchenko seriously disfigured, with lesions and discolored skin. During the interview, he appeared tired, but aides said it was the result of a long meeting to work out last-minute details for a trip to the United States that begins Sunday.

The Ukrainian leader will meet next week with President Bush at the White House and hopes to repair relations that deteriorated after the United States accused Kuchma’s regime of selling radar systems to Iraq in violation of international sanctions.

Although the sale to Iraq has not been definitively proven, Ukrainian officials recently released information about an array of shady weapons deals under Kuchma, including cruise missile sales to Iran and China.

“It was not easy for me and my government to publicly announce facts about such dealings shortly before the trip to the U.S.,” Yushchenko said. He said he and Bush would “review all the steps aimed at ending such practices.”