Ukrainian President Leonid Kuchma said his government had agreed with the opposition's demand to sack the electoral commission, but said current Prime Minister Viktor Yanukovich would not stand down.
Earlier, Ukraine's opposition said it had reached a deal that could end a stand-off with the outgoing government, paving the way for a re-run of rigged presidential polls.
"If all agreements made today are carried out, tomorrow (Tuesday) there's a big likelihood that we will pass changes in the constitution, pass changes to the election law, that the government will resign and there will be another central election commission," said opposition leader Petro Poroshenko.
Moscow-backed Yanukovich was declared winner of November's presidential elections, plunging the former Soviet state into a fortnight of mass demonstrations in support of West-leaning challenger Viktor Yushchenko.
The country's supreme court ruled last week that the poll had been rigged.
The opposition had demanded changes to the election law and election commission to prevent vote rigging in a repeat of the final round run-off due on 26 December, as well as the dismissal of Yanukovich after a no confidence vote in parliament.
Kuchma was reported to have made the demands conditional on passing constitutional reforms that would trim the president's powers - a deal pro-Yushchenko parliamentarians had rejected on Saturday.
Yanukovich has made no mention of resignation.
Kuchma wants to transfer some
power from president to PM
He said in his first comments since the court ruling on Friday that annulled the 21 November vote that he would take a break to campaign for the new vote.
In a potential boost for Yushchenko's chances, Russian President Vladimir Putin, a key player who had previously openly backed Yanukovich, said he would work with any elected leader.
Yushchenko has urged hundreds of thousands of protesters in the streets to keep up pressure on Kuchma with mass rallies and a blockade of government offices.
The opposition said the blockades would be lifted if electoral reform was passed.
The country's already weak economy has been hit and its central bank urged the government on Monday to take measures to prevent further price rises after a surge in demand for dollars.
European Union foreign policy chief Javier Solana has started round-table mediation talks between Kuchma, Yanukovich and Yushchenko.
The Polish and Lithuanian presidents and a Russian envoy were also participating, although it was not clear what the exact agenda of the mediators was.
The European Union, which along with the US has been at odds with Russia over the crisis, backed the call for parliament and Kuchma to adopt a new election law. Putin, however, has said he opposed legal changes.
The heart of Kiev remained clogged with protesters on Monday and civil servants queued up again outside their offices to see if the protesters would let them through.
"The whole system has been paralysed. It's like a broken computer," said one of several hundred finance ministry officials blocked by protesters from entering her office.