By Jeff Franks

HAVANA (Reuters) - Colombia's Marxist-led FARC rebels opened their latest round of peace talks with the government on Tuesday with a proposal to delay elections scheduled for 2014 by a year, which the government quickly rejected.

The two sides have been meeting in Havana intermittently since November, trying to end a nearly half century-long conflict in which at least 100,000 people have died and millions have been displaced.

Before entering the talks, FARC lead negotiator Ivan Marquez read a statement expressing irritation with government pressure to reach a peace accord quickly and calling for the postponement of elections to put "the collective interest of peace ahead of any other circumstance."

President Juan Manuel Santos, who has hinted he will seek another term in office in 2014, is pushing for the talks to finish this year, which the rebels frequently have complained is too fast.

Marquez also called for a national popular assembly "to find a true solution to the conflict."

But government lead negotiator Humberto de la Calle stuck to the government's line on the need to move along and dismissed both proposals.

"That won't happen," he said.

The FARC, or Revolutionary Armed Forces of Colombia, was founded in 1964 as a communist agrarian reform movement.

It appeared last month to achieve some of its key goals with the first accord of the talks calling for economic and social development of rural areas and the providing of land to the people living there.

Now the rebels and government move on to another principal goal of the discussions - turning the FARC from insurgents into political participants - which may not be easy as negotiators attempt to balance the desire for peace with calls for justice.

Many Colombians feel the rebels should face justice for war casualties, the use of kidnappings to extort money and involvement in the illicit drug trade, the latter a charge the group has denied.

But criminal charges and jail time for FARC leaders could exclude them from taking part in the political process.

The rebels have said they are willing to "review" any "error" committed during the war, but have ruled out prosecution by a state they accuse of persecuting and neglecting its own people.

De la Calle said the discussions would be about the FARC "as a whole, not about individual persons or cases" and with the guiding principle that "ideas, not arms, rule."

Other remaining issues in the talks include the logistics of ending the conflict, the drug trade, compensation for victims and implementation of the final accord.

Santos initiated the peace talks last year in the belief that the FARC had been so weakened by the government's 10-year, U.S.-backed offensive against the group that its leaders were ready to negotiate an end to the fighting.

Three previous peace attempts, the last ending in 2002, have failed.

The rebels have been pushed into far corners of the country but can still attack oil and mining operations vital to Colombia's economic growth.

Norway and Cuba are serving as guarantors for the Colombia-FARC talks, with Chile and Venezuela as observers.

Venezuelan President Nicolas Maduro threatened to withdraw his government's representative in a dust-up last week after Santos met with Venezuelan opposition leader Henrique Capriles.

In his remarks on Tuesday, de la Calle thanked all four countries, including Venezuela, for their efforts in creating a "climate of confidence" in the talks.

(Editing by David Adams and Paul Simao)