Mr. Yanukovich has made integrating with Europe a central goal, and he is likely to head off catastrophic damage by softening Ms. Tymoshenko’s conviction swiftly. One route to this would be decriminalizing the article under which she was convicted. In that event, her name would be cleared and she would be able to run in parliamentary elections in 2012, said Serhiy Vlasenko, one of her lawyers. This could occur as soon as next week, so that Mr. Yanukovich would be welcome at European Union talks in Brussels scheduled for Oct. 20.

He suggested as much on Tuesday, when he told journalists, “This is not a final decision.”

“Ahead lies the appeals court, and it will without a doubt make a decision within the bounds of the law, but the decision will have great significance,” he said, in comments carried by the Interfax news agency.

In Brussels, Ukraine’s foreign minister emphasized the progress that the country has made toward meeting European benchmarks, saying the parties “have never been so close to the association agreement as they are now.” A Foreign Ministry statement argued strenuously against linking the Tymoshenko verdict with the European Union procedure, making the case that political leaders like Mr. Yanukovich could not interfere in judicial processes. As news of the verdict spread on Tuesday, though, some in Kiev said Ms. Tymoshenko’s conviction was already marked in Ukraine’s history.

Critics of the verdict warned that Ukraine could follow the pattern set by Belarus, whose nascent engagement with the West came to an abrupt end last year amid a crackdown on opposition figures.