Ukraine's opposition Sunday intensified pressure for a quick passage of anti-fraud legislatureto ensure a fair re-run of the presidential poll after parliament failed to adopt such reforms on Saturday.

In an interview with BBC television, opposition leader Viktor Yushchenko said the voting reforms they are demanding were necessary in order to "safeguard the election process" in the new poll.

"We're trying to introduce a law which would make it impossibleto vote at home or to vote by proxy, and also to regulate the staffing of local election commissions so that we have an equal number of representatives from both sides," said Yushchenko.

The West-leaning presidential hopeful said there is still "a bit of concern" that the voting in the new poll would be transparent and democratic.

Yulia Tymoshenko, one of Yushchenko's closest allies, said the people who massed for two weeks in the capital's streets would notleave until a re-run was held on Dec. 26 and proven to be free andfair.

"Something has changed, thanks to the people," she said.

In parliament, a loose coalition of communists, socialists, andpro-government lawmakers said electoral changes won't be possible until the opposition accept constitutional reform that would transfer some presidential powers to parliament.

Opposition supporters Sunday began a massive signing-up to volunteer for monitoring work in the new poll to ensure fair votes.

Demonstrators have begun to fill out questionnaires for jobs asmonitors or election commission members. Thousands have volunteered to work as monitors and activists in areas where the Moscow-backed Prime Minister Viktor Yanukovich is popular.

Meanwhile, Yushchenko urged supporters to keep up street pressures and maintain a blockade of government buildings until clear steps were adopted to get rid of irregularities in the re-run.

Apart from electoral changes, the opposition leader also insists that outgoing President Leonid Kuchma sack the Yanukovich government and replace members of the elections commission.

"Until these decisions are taken, there cannot be any talk of lifting the picketing of the government buildings or presidential palace," Yushchenko told supporters in Independence Square in downtown Kiev.

Daritusz Szymczcha, aide to Polish President Aleksander Kwasniewski, said Sunday that the president will take part in the third round of mediation talks on Monday to help solve the Ukrainian crisis.

The president will fly to Kiev to join the third Ukrainian round table, he said.

Kwasniewski has twice traveled to Kiev following the contested Nov. 21 elections, which Ukraine's Supreme Court ruled on Friday invalid for fraud.

The United States, the European Union and the Organization for Security and Cooperation in Europe welcomed the court decision, while Russia refrained from immediate comment.

Elections in Ukraine have pitted the West against Russia. Russian President Vladimir Putin visited the country twice in the run-up to the November elections to show support for Yanukovich.