BERLIN (Reuters) - Volkswagen management and labour representatives will resume high pressure talks on Tuesday morning over planned cost cuts to the carmaker's German sites after a 13-hour negotiation round on Monday failed to produce an agreement.

Unions said late on Monday night that it was still "far from clear" whether Tuesday's talks would bring the two sides closer to one another or reach a stalemate, with unions adamant that any solution must exclude plant closures and the carmaker insisting it cannot rule them out.

Both sides had expected the talks to last several days in a last-ditch attempt to reach an agreement before Christmas and avoid the conflict, which erupted the formerly peaceful relationship between works council chief Daniela Cavallo and Chief Executive Oliver Blume, from dragging into next year.

Unions have threatened unprecedented strike action in the new year if a deal is not reached this week.

"Workers don't want to go into Christmas in fear," works council chief Daniela Cavallo told union members outside the hotel before talks began early on Monday, the fifth round since early September.