* Catalan leaders in court for politically charged trial
* Face charges of sedition over 2017 independence bid
* Bid triggered Spain's biggest crisis in decades
* Defendants' supporters says they are political prisoners
* Government says they broke the law, trial non-political (Adds protests outside court, Sanchez comment)
By Jose Elías Rodríguez
MADRID, Feb 12 (Reuters) - Twelve Catalan secessionist leaders arrived at Spain's Supreme Court on Tuesday to be charged for their role in a failed independence bid that split the country, as pro- and anti-separatist protesters faced off outside.
The defendants face charges of rebellion, sedition and misuse of public funds, after an independence declaration 16 months ago that triggered Spain's biggest political crisis in decades.
The trial will be transmitted live on national television.
The separatist leaders were driven from the Soto del Real prison outside Madrid, where they have been detained, to the court early on Tuesday morning in two vans flanked by police cars.
Hundreds of police, including from anti-terrorism units, were deployed around the court building and separatist supporters faced heckling from anti-independence demonstrators as crowds gathered there ahead of the trial.
Standing outside, pro-separatists carried signs reading "Freedom for political prisoners" while a small group opposing them shouted "Golpista" or "coup plotter", accusing Catalan separatists of having attempted to dismantle the Spanish state by declaring independence.
The defendants are not scheduled to speak in court on the first day of the trial, which is reserved for procedural issues. Nine of them have been jailed without bail since late 2017 or early 2018.
Meanwhile, seven other politicians involved in the October 2017 independence declaration are in self-imposed exile throughout Europe.
"Exile and prison are two sides of the same coin which is the repression of a political idea," Catalonia regional parliament speaker Roger Torrent said on RNE radio.
The 2017 attempt to declare Catalonia's independence followed a referendum that had been carried out in defiance of a judicial ban, and angered much of the rest of Spain.
But there was shock at home as well as abroad when police used batons and rubber bullets on protesters on the day of the vote.
BUDGET BILL BACKDROP
The trial comes at a tricky time for Socialist Prime Minister Pedro Sanchez, who needs the votes of Catalan secessionist parties to pass a budget bill that is pivotal for his administration through parliament.
Sanchez has adopted a more conciliatory tone with Catalan nationalists than the conservative government that preceded him, and tried to establish talks.
But they have in return so far vowed to block the budget bill, citing the prime minister's refusal to discuss independence.
Failure to approve the budget would likely prompt a snap parliamentary election.
"Working within the Constitution, the PSOE (Socialist party) proposed a regional policy commission in Parliament and a cross-party table in the Catalan Parliament. The right wing never participated. The secessionists never believed in them. They prefer confrontation. They're afraid of dialogue," Sanchez said in a tweet on Tuesday.
Supporters of the defendants say they are political prisoners and that the trial itself is political.
"The world is looking at Madrid ... what they want is not to judge but to condemn (for) political reasons," Olivier Peter, a lawyer for one of the accused, told reporters on Monday.
The government rejects this, saying the defendants have broken the law and judges are handling the case without political interference, in line with the rule of law.
Secessionists have called on Catalans to briefly stop work at midday on Tuesday in protest against the trial, and to join a rally in Barcelona in the evening. Another big demonstration is planned for Saturday and a general strike on Feb. 21.
The public prosecutor is seeking prison terms of up to 25 years.
The Geneva-based International Commission of Jurists, a human rights group of judges and lawyers, said the case risked restricting rights and could set a precedent. (Additional reporting by Joan Faus in Barcelona Writing by Andrei Khalip and Paul Day Editing by Ingrid Melander and John Stonestreet)
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