MADRID (Reuters) - Spanish lawmakers head to Parliament on Saturday for several days of debate ahead of an extremely tight vote that could confirm Socialist leader Pedro Sanchez as prime minister, breaking the country’s political impasse and setting the stage for a leftist coalition to enter government.

Spain's acting Prime Minister Pedro Sanchez reacts as he attends the first session of the Parliament following a general election in Madrid, Spain December 3, 2019. REUTERS/Juan Medina

After two elections in 2019 failed to deliver a clear winner, acting Prime Minister Sanchez struck a deal with far-left Unidas Podemos, but their combined 155 parliamentary seats are not enough for a majority in Spain’s highly fragmented 350-seat parliament.

With the conservative People’s Party and far-right Vox -- the second and third largest parties -- refusing to back the coalition, victory for Sanchez hinges on the votes of small regional parties that each control a handful of seats.

Catalonia’s largest separatist party, Esquerra Republica de Catalunya (ERC), on Thursday agreed to abstain from voting after Sanchez agreed to hold a dialogue over the future of Catalonia if he is confirmed. He agreed to submit the dialogue’s conclusions to Catalan voters.

But a last-minute decision by Spain’s electoral board to block ERC’s jailed leader Oriol Junqueras from becoming a member of the European Parliament has called the party’s support into question. The board also decided to strip the head of Catalonia’s regional government Quim Torra - an ERC ally - of his position as a regional lawmaker.

Lawmakers will start debating support to the coalition on Saturday at 9 a.m. (0800 GMT).

In the first vote scheduled on Sunday afternoon, Sanchez needs an absolute majority of 176 members voting in favor of the motion, a remote possibility at this point. However, he is likely to be more successful in a second round of voting set to take place on Tuesday, for which the Socialist leader will only need more votes in favor than against.

Abstention from Catalonia’s ERC should secure this.

If confirmed, the PSOE-Podemos coalition would propose corporate tax increases, more worker-friendly labor legislation and policies aimed to fight climate change and promote gender equality.

However, the government would struggle to push through any legislation given its likely razor thin majority.