A Ukrainian judge sentenced a former prime minister to seven years in prison Tuesday, harming the nation’s prospects for democracy and confronting the United States and Europe with a serious challenge.

Both have been warning Ukrainian President Viktor Yanukovych against pursuing the prosecution of former prime minister Yulia Tymoshenko, calling it politically motivated. If they fail to respond forcefully, the West could well be accused of standing by as Ukraine broke the promises of its 2004 Orange Revolution.

“Now how is the West going to react?” asked David J. Kramer, president of Freedom House and a former high-level State Department official. “Unless the statements add up to something and there are real consequences, it will send a signal to all countries in the region that they can get away with this.”

Tymoshenko had been charged with abuse of office over a deal she signed as prime minister in 2009 to buy natural gas from Russia. The agreement, pegged to the price of oil, turned out to be costly when oil prices rose. In finding her guilty, Judge Rodion Kireyev fined Tymoshenko $190 million, the amount he said the deal cost the country. He also prohibited her from holding office for three years after finishing her prison term.

“The whole process started as revenge against Tymoshenko,” said Olga Shumylo-Tapiola, a visiting scholar at Carnegie Europe in Brussels who researches European Union and Russian policy toward Ukraine. “It definitely shows the judiciary is controlled by the presidential administration and people close to it, and it’s difficult to see how democracy will return to Ukraine.”

Earlier this year, Freedom House — organized in 1941 to promote democracy and human rights — downgraded Ukraine from a free to partly free country. After he visited soon afterward, Kramer reported that Ukraine was at a pivotal point when it could develop democracy or retreat to authoritarianism.

He said Tuesday that the time is overdue for the West to push hard.

“It’s more than Tymoshenko,” he said. “Others are in jail. It’s the government trying to cripple opponents and exclude them from the political process. And it’s something the E.U. and the U.S. should not tolerate.”

The White House issued a statement saying it was “deeply disappointed” with the verdict, calling the prosecution politically motivated and urging the release of Tymoshenko and other former officials.

Members of the European Parliament’s Foreign Affairs Committee, meeting in Brussels with Ukrainian Foreign Minister Kostyantyn Gryshchenko, called the verdict a violation of the rule of law. Several suggested that they should break off negotiations on greater cooperation through what is called an Association Agreement, a treaty that was expected to be initialed soon by the E.U. and Ukraine.

Shumylo-Tapiola said E.U. states are split, with some saying signing the agreement would betray European values and others arguing that Ukraine would be driven toward Russia if Europe turned away.

Yanukovych has often been considered more sympathetic to Russia but has been pressing hard for greater integration with Europe, provoking suggestions that he is simply trying to play the two off each other for his own benefit.

Tymoshenko has been in jail since Aug. 5, after the judge took exception to her frequent critical remarks during the trial. Now 50, she was one of the leaders of Ukraine’s Orange Revolution and rose to power after popular protest overturned a fraudulent election that had made Yanukovych president. Instead, Viktor Yushchenko, a Tymoshenko ally, won the presidency. Tymoshenko was prime minister in 2005 and again from December 2007 to March 2010. Once in power, however, the democrats bickered, unable to unite the country or to subdue corruption. Many voters became disenchanted.

Yanukovych blamed Tymoshenko for costing him the election. He regained his footing in early 2010 and defeated Tymoshenko in a presidential election. She was soon under investigation on various charges, all of which were dismissed. Eventually, the gas deal prosecution stuck.

Those charges didn’t involve corruption, said Grigory Perepelitsa, an independent political analyst in Kiev, Ukraine’s capital. They had to do with political decisions, he said, and her conviction sets a precedent for making a criminal case out of a political mistake. “Now we have a precedent for bringing to liability everyone who signed the agreement,” he said.

Tymoshenko compared the ruling to Stalinist times. “The year 1937 has returned to Ukraine with this verdict and all the repression of citizens,” she said.

Tymoshenko, who wears her blond hair in braids wrapped around her head as if modeled on a Ukrainian folk tale, said she would appeal.

“We will fight and defend my good name in the European Court,” she said, vowing to fight for her political views as well. “Unfortunately, if we do not rise to the defense of our Ukraine, the great power and its state system will be lost,” she said.

Yanukovych still has a chance to back off if the conviction is reversed on appeal or if the parliament decriminalizes bad decision-making.

“If he lets her rot in jail,” Kramer said, “this could be a serious turning point for Ukraine.”