Policemen arrest former Ukrainian Prime Minister Yulia Tymoshenko, center rear, in the Pecherskiy District Court in Kiev, Ukraine, Friday, Aug. 5, 2011

Ignoring American, European and Russian criticism, a Ukrainian judge kept the nation?s leading opposition politician, Yulia Tymoshenko, in jail Monday and proceeded with her court trial.

European officials said the trial could endanger a trade association treaty that Ukraine?s president, Viktor Yanukovych, wants with the European Union.

Known for her trademark golden braid, Ms. Tymoshenko was expected to be the main opposition candidate in next year?s presidential elections.  But if she is convicted, she will not be eligible to run.

Oleh Soskin, who directs the Institute of Society Transformation, a Kyiv think tank, said that Mr. Yanukovych seeks to ?liquidate? his chief political rival while the nation is on vacation.  Soskin, like many Kyiv residents, was at his summer vacation home Monday.

As he spoke, several hundred supporters of Ms. Tymoshenko pitched tents near the downtown Kyiv courthouse, waving flags and chanting, ?Yulia, we are with you.?

But Natasha Lysova, a Tymoshenko spokeswoman, worried that summer holidays and government pressure will keep the crowds low.

?Problems for people from the regions to come here, some restrictions from the government for drivers of the buses, for owners of the buses, people cannot just come here,? Lysova said.

While Tymoshenko supporters chanted, ?Hands off Tymoshenko,? government supporters chanted, "Yulia, sweat it out in jail."

Government spokespeople say Ms.Tymoshenko is one of 400 former officials under investigation for crimes committed while in office.  But critics say the only cases that have come to trial involve opposition figures.

The Obama administration has warned Ukraine about ?selective justice.?

In the trial, Ms. Tymoshenko earned the judge?s enmity by calling him ?a monster? and the trial a ?farce.?

Over the weekend, she had to share her cell with an inmate who smoked, and she had to comply with prison regulations and let her hair down.

But by Monday morning, her braids were back in place, and she was unbowed.  When the judge walked in, she said, "I will not stand in front of you because it would be kneeling in front of the mafia.  You are not breaking me but Ukraine's young democracy."

On Friday, her arrest stemmed from mocking a witness, current Prime Minister Mykola Azarov, for speaking in Russian, rather than Ukrainian.

Ms. Tymoshenko is charged with abuse of power in connection with a 2009 deal that ended Russia?s midwinter gas cutoff to Ukraine.  Then-prime minister Tymoshenko flew to Moscow and hammered out a deal with Prime Minister Vladimir Putin.  The Yanukovych government says she broke the law by not consulting her government when signing the deal, an accord which cost Ukraine an extra $190 million.

Analysts say the Kremlin criticizes the trial, partly because Prime Minister Putin?s signature is on the gas deal and partly because Russia does not want to lower gas prices for Ukraine.

On Thursday, President Yanukovych is to break his Crimea vacation and fly across the Black Sea to meet in Sochi with Russian President Dmitry Medvedev.  The Kremlin is inviting Ukraine to join Russia, Belarus and Kazakhstan in a new customs union, an economic grouping that some call "Soviet Union lite."

The meeting will be watched closely by defenders of democracy and by advocates of a Ukrainian free trade pact with the European Union.