Kristen Stewart is said to be "pulling out all the stops" in her bid to win back the affection of boyfriend Robert Pattinson who she has cheated on.

The 22-year-old Twilight actress has admitted to having an affair with her Snow White and the Huntsman director Rupert Sanders, 41, and has issued a public apology to her beau of nearly four years.

But RadarOnline reports that despite the current pain and heartbreak caused by her infidelity, the actress believes she can patch up her relationship with the British star.

"Kristen is pulling out all the stops with Rob, completely apologising and trying to make things right with him," a source told the site.

"But she is very confident that she is going to win his trust back.

"Kristen is doing everything in her power to keep Rob from breaking up with her. She knows how much he loves her and she really believes that she is going to keep him from dumping her."

Kristen and Rupert were snapped last week kissing and caressing in her car. He has also since apologised to his model wife Liberty Ross with whom he has two children.