Caracas (AFP) - Venezuela's opposition said Saturday it would not resume stalled talks with the government next month over their country's grave crisis because a number of demands had not been met.

"Conditions do not exist for the return to direct dialogue between the parties on January 13," the secretary of the MUD opposition coalition, Jesus Torrealba, said.

He was responding to a letter from the Vatican which, along with the UNASUR bloc of South American nations, is attempting to forge a consensus to tackle Venezuela's dire economic and political situation.

President Nicolas Maduro's government has already rejected the Vatican letter's urging that talks restart on January 13, calling it an "ultimatum."

According to Torrealba, the letter called for an electoral calendar to "allow Venezuelans to decide their future without delays."

Such language would imply early elections to replace Maduro -- something the president has fiercely resisted despite him suffering deep unpopularity.

The opposition is demanding that the talks result in the setting of a recall referendum against Maduro or that presidential elections due for December 2018 be brought forward.