MADRID (Reuters) - Tension rose between acting Prime Minister Pedro Sanchez’s Socialists and far-left Podemos late on Wednesday, with one side saying Podemos’ demands were unacceptable and the other seeing no coalition deal before a vote in parliament on Thursday.

Slideshow ( 2 images )

Sanchez, who won an April parliamentary election but fell short of a majority, needs the support of Podemos, as well as the abstention or support of at least one other smaller party, to be confirmed as prime minister.

If Sanchez is not voted in as prime minister on Thursday, new votes could be held in September. A senior source in Podemos told Reuters: “We’re going to September.”

If there is no government by late September, a repeat election would be held in November.

The two parties would in theory still have two months to negotiate a deal if Sanchez loses Thursday’s vote. But earlier this month, the Socialists said they would give up trying to install Sanchez if he failed to win the July parliamentary vote.

Two government sources told Reuters that Podemos’ demands were “unacceptable,” pointing to a series of high-level cabinet positions demanded by the party in exchange for its support in a document shared widely with press.

But while El Pais daily newspaper wrote on its website that the government considered the talks had broken off, the two government sources did not confirm that to Reuters.

One suggested the door was still somewhat open, referring to Podemos and saying: “They must change their mind and hear reason.”

The vote is expected at around 2:30 pm (1230 GMT) on Thursday and much can still change before then. The mood has shifted several times over the past days, with the two parties seeming at times very close to a deal only to say they were on the brink of breaking off soon after.

Another Podemos source said late on Wednesday evening that the party was still backing a coalition government but criticized the Socialists’ approach to negotiations after several negotiating documents were leaked.

“Today, with only hours until the second vote, we see the Socialists trying to burn all bridges and leak to the public various documents,” the source said.

Podemos will not enter the government “at any cost,” the source added, saying party supporters wanted cabinet positions that would allow them to act on a series of policies including labor and budget.