The board of directors initially intended to reject the loan on Wednesday, the daily Žurnal reported last week.

However, after receiving a letter from Anton Rop, the Slovenian EIB vice president, they postponed the decision to review the environmental and economic sustainability of the EUR 1.3bn project and make sure of the state guarantee's credibility, the paper said.

The daily Delo said the doubts may have been spurred by signs of possible corruption in the project, which three MEPs and environmental NGOs had warned the EIB was indicated in January's resignation of Simon Tot as TEŠ director.

Acting TEŠ director Franc Rosec told the STA on Monday that TEŠ had not been notified of the developments regarding the loan, but they expect the loan to be approved by the end of the month based on prior reviews of the project.

Slovenia's biggest energy project has been delayed several times in the past, most notably with the long parliamentary procedure for the approval of the state guarantee, which eventually stepped into force at the end of 2012.