Opposition leader Viktor Yushchenko said on Friday he would prosecute government officials and their supporters for crimes committed during the last decade should he win Ukraine's Dec. 26 repeat of the presidential election.

Meanwhile, Russian President Vladimir Putin — who backs Yushchenko's opponent — said Moscow has no objection to Ukraine joining the European Union (search). The comments were in marked contrast to several weeks of harsh rhetoric from Putin, who has warned the West not to meddle in Ukraine's elections crisis.

"If Ukraine wants to enter the EU and is welcomed there, then we can only be pleased," Putin said, speaking after meeting with Spanish Prime Minister Jose Luis Rodriguez Zapatero (search). "The issues of EU enlargement to include Ukraine does not concern us."

Yushchenko (search) wants to strengthen Ukrainian ties with Western Europe, pulling away from its centuries-old position in Russia's sphere of influence. The opposition leader's promises Friday to prosecute past crimes underlined his campaign as a reformer in the race with government candidate Prime Minister Viktor Yanukovych.

Yushchenko singled out the murder of journalist Hrihoriy Gongadze as an example of a crime that will not go unpunished should he be elected. Ukraine's President Leonid Kuchma was accused of involvement in the case, although he has denied the allegations.

"I have a moral obligation to Gia," Yushchenko said, using the journalist's nickname. "Those guilty will be prosecuted — not only this, but other important cases."

With the momentum of more than two weeks of street protests behind him, a confident Yushchenko pledged not to engage in purely political retaliation against his opponents should he win.

Yushchenko spoke as the two sides started mapping out their campaign strategies for the the repeat of the Nov. 21 run-off vote. The Supreme Court threw out Yanukovych's victory in that runoff, saying it was invalidated by fraud. Yushchenko's comments came in his first press conference since parliament voted to grant key electoral changes aimed at averting fraud. The measure also handed over some presidential powers to the parliament.

Meanwhile, Yanukovych's native Donetsk region agreed to cancel a referendum on self-rule planned for early January. In a joint statement, Donetsk and other eastern provinces that supported Yanukovych in the runoff promised to abstain from such plans, which stoked fears of the country's breakup.

The opposition continued dismantling its blockades of government offices following the parliament's passage of the electoral changes Yushchenko had demanded.

A few dozen protesters maintained a vigil outside the president's office. More protesters milled around the tent city set up by Yushchenko's supporters along the city's main avenue, but thousands of their comrades returned to their homes, schools and offices after spending more than two weeks in street protests.

"The revolution is far from over but some simply had to go back to work," said Vyacheslav Godunyk, a clerk from Kiev. "We can be back on streets in minutes."

Only a handful of protesters remained in place after barricades were dismantled Thursday outside the gray, Stalin-era Cabinet building. The blockade, an opposition tool to keep up pressure on the government, had kept top officials from reporting to work.

"This is a sad and happy day at the same time," said Oleksiy, a protester who gave only his first name. "We endured more than two weeks and now we are leaving, but we are leaving as winners."

A blockade near the president's office remained in place, but Roman Zvarych, a member of Yushchenko's campaign staff, said he believed it, too, would soon be removed.

Tension in Ukraine's political crisis has abated with parliament's adoption Wednesday of the electoral changes in return for handing over some presidential powers to the parliament.

Yushchenko's campaign chief, Oleksandr Zinchenko, said his camp would now focus on southern and eastern regions where Yanukovych drew most of his votes.

Also Friday, Kuchma named a new prosecutor general, Svyatoslav Piskun. He replaces Hennady Vasylyev, who was accused by Yushchenko's supporters of covering up election fraud.