Ukraine's President Petro Poroshenko plans to start talks on forming a coalition government after exit polls showed his bloc emerge strongest in Sunday's parliamentary elections.
He said talks might last up to 10 days.
PM Arseniy Yatseniuk's People's Front party could be a key partner, he added.
Pro-Western parties look set to dominate parliament after the first legislative polls since the pro-Russian former President, Viktor Yanukovych, was driven from power in February.
No votes were cast in two areas under control of pro-Russian separatists in the east of Ukraine, with 27 parliamentary seats there and in Crimea - annexed by Russia in March - remaining vacant.
Preliminary official results are expected later on Monday.
However, exit polls indicated that President Poroshenko's bloc - comprising his own Solidarity Party and Udar, led by former boxer champion Vitali Klitschko - was in the lead with about 23% of the vote.
"More than three-quarters of voters who took part in the polls gave strong and irreversible backing to Ukraine's path to Europe," Mr Poroshenko said in televised comments.
He said that in order not to lose time, coalition consultations should start on Monday.
"We have these 10 days when we must create... the best government in Ukraine because no other government will cope with the challenges that the country is facing today," he added.
At least 3,700 people have been killed since an insurgency in the east of Ukraine began earlier this year.
Despite a truce agreed on 5 September some 300 people have been killed in sporadic clashes between the Ukrainian army and pro-Russian separatists around Donetsk's airport.
Correspondents say that the top three performing blocs, including those of Mr Poroshenko's and Mr Yatseniuk, are strongly pro-European and are likely to give the president a strong mandate to pursue democratic reforms and pursue efforts to end the conflict in the east.
The exit polls suggested Mr Yatseniuk's People's Front would come second, with around 21% of the vote, and the Self Help Party, based in western Ukraine, third with more than 13%.
Parties linked to the government of former President Yanukovych or with close ties to Russia were set to receive fewer votes, the polls indicated.
The Opposition Bloc, formed by allies of ousted Pro-Russia President Viktor Yanukovych, was fourth with 8%, while the pro-Russian Communist Party might be without representation in parliament for the first time.
However, the exit polls only take into account voting for 225 of the 450 seats.
(BBC)