Exit polls gave opposition leader Viktor Yushchenko about a 15 percentage point advantage over Prime Minister Viktor Yanukovich in the re-run of the Nov. 21 election that was annulled due to mass fraud.
"Local election commissions have been working for only six to 10 days. We were not able to teach them fully. But I think we will be able to determine the results rather quickly," Yaroslav Davydovych said on Sunday.
"I think we will know the preliminary results by morning."
The commission has counted 2.48% of ballots so far, mostly from polling stations abroad. Yushchenko had won 69.69% and Yanukovich 27.11% so far, election officials said.
Most polls showed the pro-West
Yushchenko in the lead
Prime Minister Viktor Yanukovich, whom exit polls show losing Ukraine's presidential election on Sunday by a wide margin, vowed to lead a "tough opposition" if his liberal opponent Viktor Yushchenko is the winner.
"There will be no talks," Yanukovich told reporters after exit polls put Yushchenko on top.
"If I lose, there will be a tough opposition. They will see what an opposition means."
A respected Ukrainian non-government organization specializing in election monitoring said that it did not detect massive violations during a historic rerun presidential vote.
"According to preliminary results, we can say that there were no massive falsifications," the Committee of Ukraine Voters said in a statement released after the close of polls.
The NGO had deployed 10,000 observers to monitor Sunday's rematch with Western-leaning opposition leader Viktor Yushchenko and his pro-Russia rival Viktor Yanukovich.
An unprecendent 12,542 observers had registered to monitor Sunday's election.