The president, who had earlier extended the assembly's deadline until the end of Thursday, warned that if deputies failed to pass the necessary laws, his allies in the chamber would immediately give up their seats.
"So the election will be held automatically within 60 days - this is a clause in the constitution," he said.
Parliament proceeded slowly with the package on Thursday, giving initial approval to budget changes, including financing for the election.
Oleksander Moroz, the parliamentary speaker, said final approval might not be forthcoming until Friday.
EU urges non-violence
European Parliament members called on all sides in the dispute to "concentrate on agreements, not disagreements".
After meeting the country's senior leaders, Adrian Severin, head of the EU assembly's ad hoc mission, said: "The latest agreement was a very important step, but it did not entirely address the root causes of the recent political crisis."
|"The latest agreement was a very important step, but it did not entirely address the root causes of the recent political crisis"|
Adrian Severin, head of the EU assembly's ad hoc mission to Ukraine
He urged leaders to avoid violence and said such action would "dramatically damage Ukraine's European prospects".
The pro-Western Yushchenko has promoted long-term European Union and Nato membership since defeating Yanukovich in the rerun of a rigged 2004 presidential poll.
European leaders, who backed Yushchenko in his allegations of electoral fraud in the 2004 protests, have this time taken no sides and expressed dismay at the protracted crisis.
Yushchenko dissolved parliament by decree last month and ordered the poll, but a date was set only after much wrangling.
The president on Wednesday accused "certain forces" of trying to derail the election. He had originally suspended his decree to give the fractious parliament two days - Tuesday and Wednesday - to approve the legislative package.
Debate on Wednesday bogged down when Yanukovich's allies objected to the president's call to bar parliamentarians from switching parties once elected.
Yushchenko called the poll after accusing Yanukovich, whose power base is in Russian-speaking eastern Ukraine, of illegally poaching supporters to expand his majority in parliament and change the constitution.