The Ukrainian government has officially named Volodymyr Hroysman as the country's acting prime minister.
In its statement issued on July 25, the government said the decision had been made due to Prime Minister Arseniy Yatsenyuk's resignation.
But Ukraine's parliament said it has not yet received a resignation letter from Yatsenyuk and could therefore not vote on whether to accept his resignation.
Hroysman, 36, has been serving as Yatsenyuk's deputy prime minister and regional development minister since February.
Yatsenyuk said he was resigning in parliament on July 24, explaining that the parliamentary coalition’s breakup earlier that day led to the "blocking of the cabinet's initiatives."
Two parties in the majority coalition announced their withdrawal to allow President Petro Poroshenko to start the procedure for new parliamentary elections.
Early parliamentary elections were expected since the February ouster of former President Viktor Yanukovych following months of protests.
Hroysman was elected mayor of the western city of Vinnytsia in 2006.