CARACAS, April 10 (Reuters) - President Nicolas Maduro was due to host Venezuelan opposition leaders on Thursday night at the start of mediated talks intended to stem violent protests in which dozens of people have died in the OPEC nation's worst unrest for years.
Some hardline opposition groups, including the party of jailed protest leader Leopoldo Lopez, are boycotting the dialogue while demonstrators remain in jail.
The meeting, brokered by foreign ministers from the Unasur bloc of South American governments, was expected to start at 8 p.m. (0030 GMT) at the Miraflores presidential palace in Caracas and be broadcast live on state TV.
Both sides have also asked the Roman Catholic Church to attend as a "good faith" witness. The Vatican has confirmed its willingness to mediate but not named an envoy to the talks.
"Miraflores will tremble," said opposition leader Henrique Capriles, who narrowly lost to Maduro in last year's election to replace late socialist leader Hugo Chavez.
"We will tell the government the truth so that the country can open its eyes and we see that things must change," added Capriles, who is part of the Democratic Unity (MUD) opposition coalition's delegation to the talks.
Pollsters say both Maduro's and the opposition's approval levels have fallen during the recent crisis, while an already slowing economy has suffered a further drag due to the impact of violent clashes on businesses and transport.
Since protests began in early February, 39 people have died and about 600 been injured, officials say. More than 2,000 have been detained, with scores still behind bars.
Maduro, who calls himself the 'son' of Chavez and is seeking to preserve popular oil-funded welfare policies while tinkering with his predecessor's statist economic model, said ahead of the talks that he would talk but not negotiate.
"There will be no pact with anyone. There is a debate, a dialogue, which is different," he said. "I would be a traitor if I start negotiating the revolution."
Hardline protesters have openly sought to provoke a "Venezuelan Spring" that would force Maduro out of office but have failed to bring the millions onto the streets they had hoped for. The demonstrators have proved persistent, however, with roadblocks, marches and other protest tactics still continuing sporadically in some cities. Students in Caracas planned to rally just before the talks started.
Venezuelans across the political spectrum are fed up with violent crime and economic problems including a 57 percent annual inflation rate and shortages of basic products from milk and flour to toilet-paper and car batteries.
Both sides said those issues would figure high in the talks. (Reporting by Andrew Cawthorne and Eyanir Chinea; Editing by James Dalgleish)