Pedro Sánchez (left) says he won't join forces with Mariano Rajoy's center-right Popular Party | Gerard Julien/AFP via Getty Images Mariano Rajoy warns of third Spanish election after snub by Socialists Pedro Sánchez says he won’t join a coalition with Rajoy’s center-right.

Spain could face an unprecedented third round of elections, Prime Minister Mariano Rajoy warned Tuesday after his Socialist rival refused to join a coalition government.

Rajoy is trying to form a coalition after two elections — in December and June — failed to produce a clear winner. But Pedro Sánchez of the Socialists has repeatedly refused to join forces with Rajoy's center-right Popular Party, and did so again on Tuesday.

"If Sánchez continues to say no, we will go to repeat elections" Rajoy said, according to El País.

"Mr. Sánchez has not been responsive to my requests," Rajoy said, adding that he has offered his rival "all the time it takes to reach some kind of understanding."

"The only alternative is the repetition of elections unless Sánchez has in mind something I do not know of."

The PP came out on top at the June 26 vote but fell short of an absolute majority, winning 137 seats out of 350 while the Socialists came second with 85 seats.