With Western-leaning opposition leader Viktor Yushchenko drawing his strength from the massive street demonstrations of Ukrainians angry at the widespread fraud in the November 21 election, he needs a quick solution before his supporters are worn out by the bone-chilling winter weather.

Meanwhile pro-Moscow Prime Minister Viktor Yanukovich, the disputed winner of the election, has seen high-level defections from his camp and needs time to rally his forces for a new campaign.

After meeting Wednedsay with international mediatiors, including EU foreign policy chief Javier Solana and Polish President Aleksander Kwasniewski, the two rivals agreed to set up a working group with parliamentary experts to hammer out the legal and technical issues of holding another vote.

They agreed to wait until the supreme court delivers a ruling on the November 21 runoff vote to make key decisions on how the election process would procede.

But it is clear there is a huge chasm between their positions: Yushchenko favors holding a quick rerun of the runoff, as soon as December 19, while Yanukovich's camp favors a new vote from scratch, which would mean Ukrainians won't cast ballots for months.

On Wednesday Yushchenko appealed for his supporters to stay on the streets until an election date is named.

"We will not leave here until we know the date of the new election," he told a sea of his supporters on central Kiev's Independence Square after meeting with the foreign mediators.

Western diplomats say time is working against the opposition, warning it will be difficult for Yushchenko to keep his supporters mobilized.

"The opposition feels they must uphold the political pressure. You cannot uphold the political pressure until January," a western diplomat told AFP.

"The people felt they were cheated by a corrupt and falsified vote. They want action now and I don't know if they will wait months," said another diplomat.

Meanwhile Yanukovich's camp is in disarray. His campaign manager resigned this week, and many of his lawmakers defected and voted Wednesday for his dismissal as prime minister.

At a meeting with activists earlier this week, a Yanukovich campaign official said: "We are not ready for a third round of elections. We don't have the money."

President Leonid Kuchma, who hand-picked Yanukovich as his successor, has supported holding completely new elections, which could take as long as March to organize, and would allow him to field a new candidate, said one analyst.