Speaking during a interview with Cadena COPE radio, the conservative leader said the date for Spain going to the polls wasn't yet set in stone but that it would take place in December.
"I can't tell you the exact date yet but I can say that it will be in December," he told presenter Carlos Herrera.
"It will most probably take place on December 20th but there is also another date being considered," he added.
Entrevista en COPE pic.twitter.com/bz16KjIBsG— carlos herrera (@carlosherreracr) September 3, 2015
Rajoy faces a challenge from protest parties that have gained support in the crisis.
The latest polls show that Rajoy's Popular Party have the biggest share of the vote but fall far short of the overall majority they currently enjoy since sweeping to the power in 2011.
Protest party Podemos is in third place and could force the PP out by teaming up with the second-placed Socialists (PSOE).
That would herald a striking change in Spanish politics which has been dominated by the two big parties since the 1970s.
Rajoy has warned that would undermine Spain's economic recovery. He forecasts growth of up to 3.3 percent this year.
He cites Greece's troubles since the left-wing Syriza party, an ally of Podemos, came to power there.
Speaking of the possibilty of not winning a majority and infact being blocked from government if a pact was made between other parties, Rajoy insisted that it would be the least democratic outcome.
"It is not one of the best ways to respect the will of the citizens," he said. "Spain has always been governed by the party that wins the most support."