"Our Ukraine and the Communists as an alliance is out of question. This would be an explosive mix," Yuriy Yekhanurov said, adding that his bloc would prefer to create a coalition rather than join one.
Petro Symonenko, Communist Party leader, said earlier Thursday that his party could review its participation in the "anti-crisis" coalition if Our Ukraine joined it.
The coalition emerged in the Supreme Rada last week and was officially formed Tuesday. It comprises the largely pro-Russian Party of Regions, which won the largest share of the March 26 parliamentary election, the Socialist and the Communist parties.
Our Ukraine was a member of the previous, West-looking coalition with former Prime Minister Yulia Tymoshenko's eponymous bloc until it collapsed following the Socialists' defection.
President Viktor Yushchenko, who appealed to the Rada Thursday to end political wrangling, form a final coalition majority and decide on a candidate for the premier's job, is mediating talks on a grand coalition that could comprise the Party of Regions and Our Ukraine as the main players.