Finance Minister Jacek Rostowski will retain his post in Poland's new government and Radoslaw Sikorski will remain as foreign minister, Prime Minister Donald Tusk said on Thursday.

Tusk nominated Deputy Treasury Minister Mikolaj Budzanowski to take charge of the ministry overseeing privatisation. He previously oversaw the energy sector.

Rostowski is regarded by financial markets as a guarantor of fiscal stability in Poland, the sole member of the European Union to escape recession in recent years.

He has kept state debt under control, although central bank governor Marek Belka has joined a chorus of economists urging Tusk and Rostowski to push through ambitious fiscal reforms in their second four-year term.

I don't have any doubt that the next four years will present unprecedented challenges, Tusk told a news conference.

Tusk's centre-right Civic Platform (PO) party won an October 9 election and he will present his government programme to parliament on Friday. His cabinet is expected to be confirmed by parliament on Saturday.

Tusk remains in a coalition with the agrarian Peasants' Party, whose leader Waldemar Pawlak will retain his posts as deputy premier and economy minister.

(Reporting by Pawel Sobczak; Editing by Robert Woodward)