President Borut Pahor's office said he will next week meet Jansa to discuss the nomination. Jansa leads the Slovenian Democratic Party (SDS), which is the largest in parliament after winning an election last month.

Any delay in forming a government will push back the task of reforming the health and pensions sectors to ease the burden on state finances of an ageing population.

Pahor held a second round of talks with parties on Friday that showed that none could muster sufficient support in the fragmented parliament to win election as prime minister.

"Therefore the president will nominate for the prime minister the head of the party which gained most parliamentary seats at the recent ... election," his office said on Friday.

The SDS holds 25 out of 90 parliamentary seats and only the conservative New Slovenia (NSI) and the Slovenian Nationalist Party say they would support Jansa. Together they hold 11 seats.

Other parliamentary parties claim they will not enter coalition with the anti-immigrant SDS.

Five centre-left parties and New Slovenia are holding talks to form a coalition headed by Marjan Sarec, president of the second largest party, the List of Marjan Sarec (LMS). The six parties hold 50 seats but have failed to agree on a coalition.

"There is still a lot to negotiate," Sarec told reporters, adding that the six parties are expected to decide on whether to accept the proposed coalition agreement next week.

Analysts said it looked unlikely that Jansa would secure a majority and so he was likely to decline the nomination. SDS's spokesman Miro Petek declined to comment.

If a nominee fails to muster a majority the president and parliamentary members have 14 days to nominate the same or a new candidate.

Analysts say Slovenia will most likely end up with Sarec at the head of a centre-left government but early elections cannot be ruled out.

A priority for the next government will be preparing the sale of state-owned Nova Ljubljanska Banka (NLB). Slovenia agreed to sell it in exchange for European Commission approval of state aid to the bank in 2013.