National lawmakers are to vote on whether to allow Catalonia's regional assembly to hold a referendum on independence from Spain, as the northeastern region has vowed to do on .
The motion is set to be rejected since it is fiercely opposed by the ruling Popular Party which holds a majority in the parliament, as well as by the opposition Socialists.
" session has become a mere formality," which Catalan president Artur Mas has said he will not even attend, said Catalan political analyst Josep Ramoneda.
"In the vote they will say no, with an overwhelming majority" to a Catalan referendum, he said.
Spain's conservative Prime Minister Mariano Rajoy has insisted the referendum cannot take place and that independence would be an economic disaster for Spain and for Catalonia, one of its most productive but most indebted regions.
But Mas has vowed to hold the referendum regardless.
"The secession process will not stop. He is too committed now" to turn back, said Ramoneda.
Spain's Constitutional Court ruled last month that the move by Mas and other Catalan political leaders to unilaterally hold a referendum was unconstitutional.
But Mas vowed after that ruling: "The political process continues. Each hurdle we encounter on this road, we will find a way around."
If Spain's courts definitively block the referendum, Catalonia could hold "snap elections as a plebiscite" on independence, Ramoneda said.
Proud of their distinct language and culture, many of Catalonia's 7.5 million citizens resent the redistribution of their taxes to other regions.
The 2008 real estate crash that triggered a five-year economic downturn across Spain has added to the pressure for secession over the past two years.
On , Catalonia's national day, hundreds of thousands massed in a human chain stretching across the region to demand independence, following another rally of a similar size a year earlier.
The powerful pressure group behind that rally, the Catalan National Assembly, has drawn up a "roadmap" calling for a declaration of independence on and a new constitution on that year.
That date commemorates the conquest of Barcelona by Spanish king Philip V's forces in 1714, which many Catalans say marked the end of centuries of autonomy.
Polls have shown a majority of Catalans in favour of independence, but tensions have risen there between pro- and anti-independence elements, including prominent businessmen.
Josep Lluis Bonet, chairman of the Cava Freixenet wine group, has come out publicly against independence, while the chief executive of the Grifols pharma firm, Victor Grifols, last week encouraged Mas "not to retreat".
A report published by business experts said Catalonia's economic output risked shrinking by 10 percent over the next three years due to the uncertainties raised by the referendum drive.
Another report by experts including the economist Angel de la Fuente warned Catalan independence would have an "exorbitant" cost for the region and Spain.
De la Fuente, who was also chosen by the national government to carry out a separate study of regional financing, forecast that the stand-off could turn ugly.
He said Catalan leaders would likely make a unilateral independence declaration and get harshly sanctioned by Madrid in return.
"A transition period would occur in which the region's status would be in limbo," he said.