Ukraine's parliament has missed a deadline to pass laws to allow early elections and end a two-month crisis.
The deal was reached after marathon talks at the weekend
Parliament had two days to approve a deal between President Viktor Yushchenko and PM Viktor Yanukovych to allow the elections on 30 September.
Mr Yushchenko hinted on Wednesday that he may give lawmakers more time to consider the laws.
The two have been locked in a bitter power struggle for months. In April, the president dissolved parliament.
He has accused Mr Yanukovych of trying to usurp his power.
A bomb scare forced lawmakers to evacuate the building during the tense parliamentary session.
Mr Yanukovych has said he would seek an extension of the debate because there had not been enough time to discuss all the issues.
Speaker Oleksander Moroz said debate would resume on Thursday.
Earlier on Wednesday, Interior Minister Vasyl Tsushko - a key figure in the stalemate - suffered a heart attack, a ministry official said. His condition was still unknown.
At issue were laws on election financing, electoral commission reform and the former Soviet republic's bid to join the World Trade Organisation (WTO).
Debate centred on a call to ban politicians from switching parties once elected and a proposed minimum poll turnout.
Parliament made three attempts to pass the laws.
Earlier, Mr Yushchenko said "certain forces" were trying to prevent the election.
"For some, it would mean new corruption allegations, for others it would be political death," he said.
The election deal had been reached after a marathon 12-hour session of talks between the two leaders on Sunday. It had been hailed as a compromise solution to the country's two-month political deadlock.
Mr Yushchenko became president in January 2005 following the pro-democracy Orange Revolution, which overturned a rigged victory for Mr Yanukovych.
But Mr Yushchenko was forced to accept his rival as prime minister after his allies failed to win a majority in the March 2006 parliamentary election, and the two men have repeatedly clashed.
The president favours closer ties with the West, while the prime minister is seen as more pro-Russian.