Spain's Socialist party has signed an agreement with liberal newcomer party Ciudadanos to support the Socialists' bid to form a government but they are still way short of a majority.

With the deal signed Thursday, Socialist leader Pedro Sanchez can only count on his party's 90 seats and 40 from Ciudadanos in the 350-seat lower house of Parliament.

Both the conservative Popular Party and far-left newcomer Podemos — with 192 seats between them — have said they will vote against him.

Sanchez presents his government plans for debate in Parliament next Tuesday, and the next day faces a vote of confidence, which he must win with a majority.

If he fails, a second vote takes place two days later when he only needs more votes in favor than against.