Supporters of Ukraine's opposition leader and presidential candidate Viktor Yushchenko take part in a rally in Kiev Nov. 24, 2004. (Xinhua Photo)

Ukraine's opposition refused on Wednesday to hold negotiations with the government over the disputed presidential election after President Leonid Kuchma demanded such talks among all parties on Tuesday.

Supporters of opposition leader Viktor Yushchenko took to the streets in the capital of Kiev, pressing for installing the liberal challenger as president. They confronted riot police on Tuesday night after their candidate blamed Kuchma for fraud in the poll and proclaimed himself president.

Incomplete official results show that Prime Minister Viktor Yanukovich, Kuchma's chosen successor, poised to win Sunday's run-off between the rivals who presented different images for the former Soviet republic.

Yanukovich believes that Ukraine's future prosperity lies in close ties with Russia while Yushchenko favors gradual integration with Western Europe.

Yushchenko and international observers have said the poll was rigged while allies of Yanukovich claimed that the protests are aimed to foment unrest and seize power.

The United States said allegations of fraud had to be investigated and warned Ukraine against using force against demonstrators. The State Department summoned the Russian ambassador in Washington over Moscow's early congratulations to Yanukovich.

The two candidates were very close in the first round on Oct. 31.