HANOVER, Germany (Reuters) -Talks between Volkswagen and unions on cuts to its German operations continued through the night and into Wednesday, according to two sources familiar with negotiations, as the sides battle to reach a solution before Christmas.

The latest round of talks, which kicked off on Monday, reflects efforts by both sides to seek agreement over mass layoffs and plant closures in what has become the carmaker's biggest crisis in recent years.

There is no guarantee that talks will result in a deal, the people said, adding talks could still collapse in what has become a standoff, with unions staying firmly opposed to plant closures while VW refrains from ruling them out.

IG Metall hopes for an agreement this week to give workers peace of mind before Christmas, threatening to escalate strikes in the new year if no deal is struck.

Volkswagen declined to comment.