Oleksandr Turchynov, the head of Tymoshenko's election headquarters, said they are sure that the voters backing Tigipko, Yuschenko, Change Front head Arseniy Yatsenyuk and some other contenders in the first round will support Tymoshenko in the runoff regardless of the position of the candidates themselves.

Yanukovich, however, told a news briefing that he will not hold talks with other candidates over their support for him until the final results are published.

"I want to remind the voters against me and in favor of the current authorities that I will never repeat my predecessors' mistakes," he said.

He vowed to make every effort to keep the country strong and independent if elected. "Of course, I will improve people's living standards significantly."

Yanukovich draws the bulk of his support from the Russian-speaking areas of the industrial east and the south. He has promised Ukrainians economic revival, new jobs, pay raises, judicial reforms and tax-free policies for small enterprises for five years.

Tymoshenko, the former Yushchenko ally in the "Orange Revolution, " whose power base is in the west of the country, gave priority to a fair society and government efficiency, and pledged innovation-driven economic structure reform and improvement in people's welfare.

Viktor Yanukovych, head of Ukrainian leading opposition Regions Party, is ready to cast his ballot at a polling station in Kiev, capital of Ukraine, on Jan. 17, 2010. Ukrainian voters started to cast votes on Sunday to choose their next president out of 18 candidates. [Lu Jinbo/Xinhua]

Despite Yanukovych's leading position, Tymoshenko's extraordinary political skill makes it difficult to predict the election results, and other rivals' attitude will be crucial to the run-off, analysts say.

Ukrainians went to the polls on Sunday for the country's first presidential election since the 2004 "Orange Revolution."

Registered voters cast their ballots at 33,000 polling stations across the country and more than 3,000 international observers monitored the election, according to the Ukrainian Central Election Commission.

Polls opened at 8 a.m. (0600 GMT) and closed at 8 p.m. (1800 GMT). Official results will be published in 10 days.

Under the Ukrainian electoral laws, one candidate secures an outright victory by garnering over 50 percent of the vote in the first round. If there is no outright winner, the two top candidates will go forward to a run-off to be held three weeks after the first round.