Liberty Ross and Rupert Sanders

Rupert Sanders is seriously worried his affair with Kristin Stewart could ruin him and his marriage and thinks the well documented and photographed tryst was the ''worst mistake of his life''.

The 'Snow White and the Huntsman' director deeply regrets his secret relationship with the 'Twilight' actress and fears it could have ruined his marriage to Liberty Ross, as the model continues to refuse to forgive him and was even spotted without her wedding ring in Los Angeles this week.

An insider told RadarOnline.com: ''She is refusing to see him right now and has not spoken to him about if they have a future together or not.

''Rupert is willing to do absolutely anything and everything he can to save his marriage, he realizes this is the worst mistake of his life, and he cannot believe he was so stupid.

''The thought of losing his wife and children, who he loves more than anything in the world is killing him.''

Liberty was pictured putting on a brave face as she stepped out without her wedding ring over the weekend for the first time.

The model - who has two children Sykla, seven, and Tennyson, five with Rupert - has reportedly not seen her husband since the telltale pictures emerged of him embracing the 22-year-old brunette, and the director is now worried a reconciliation is looking ''increasingly unlikely''.

The source added: ''Liberty has told Rupert she just doesn't think she will be able to trust him again. This affair went on right under her nose and she feels like he has made her look like a fool.

''Rupert is just hoping it will blow over soon and he can win her back, but that is looking ever increasingly unlikely.''

© Bang Showbiz