PRAGUE, June 14 (Reuters) - Czech power utility CEZ handed over its recommendation for the winner of a tender to build up to four new nuclear power blocks to the government on Friday, the company and the government said.

They did not say which company had been recommended. The government will pick next month between Korea's KHNP and France's EDF, and also decide on the number of units to be built, the industry ministry said.

The plan to help wean the Czech Republic's energy system off fossil fuels and replace some ageing nuclear blocs is expected to be the country's largest investment project, estimated at tens of billions of dollars if four units are built.

CEZ said it evaluated the bids for the units of 1,000 - 1,200 megawatts each based on price per megawatt-hour of power to be produced.

Given national security considerations and the cost, which is too high for CEZ to shoulder without state aid, the government will make a final decision on the tender.

The government initially wanted one unit to be built next to the current Dukovany nuclear plant in southeastern Czech Republic, but asked the bidders in January to include an option to build one more there and up to two more at the southern Czech Temelin plant to achieve a cost reduction per unit.

"We will announce the selection of the preferred contender in July and inform about how we will use the option for the construction of additional nuclear units in Dukovany and Temelín," Industry and Trade Minister Jozef Sikela said in a statement.

The government has so far won European Union approval of state aid for the construction of the one unit in Dukovany, using low-interest loans and a scheme for pricing of produced electricity - called contract for difference - to guarantee CEZ a positive return on the project.

CEZ, which has a 30% free float, has said it could not replicate that financing model four times, and the government is yet to complete a financing plan for the potential other units. (Reporting by Jan Lopatka, Editing by Timothy Heritage)