The Twilight co-stars originally split up last summer when Stewart admitted to cheating on Pattinson with her married Snow White and the Huntsman director Rupert Sanders.
[Kristen Stewart and Robert Pattinson at the premiere of 'The Twilight Saga: Breaking Dawn - Part 2']
Pattinson told Stewart that he wanted to call time on their relationship once again over the weekend, according to The Sun.
"She flew to LA and was supposed to be Rob's date for the Golden Globes, but he told her he wants to cool it off," an insider claimed. "He loves her, but would rather go back to being good friends so they can rebuild their trust and focus on work after Twilight.
[Kristen Stewart pictured with Rupert Sanders]
"Kristen's upset but understands. She shouldn't have pushed him to reconcile after her infidelity. She's hoping he'll come round and time will be a great healer.
"He was getting so much pressure to ditch her. His friends told him to focus on his career and said she was wrecking his chances."
[Robert Pattinson and Kristen Stewart in a scene from 'The Twilight Saga: Breaking Dawn - Part 2']
The couple reconciled in September, but were recently rumoured to have been "fighting a lot", with Cosmopolis actor Pattinson said to be feeling "unhappy" in the relationship.
Stewart is reportedly planning to move to New York for a fresh start, with a second source claiming that the On the Road actress feels she "has a bit more peace" there than in Hollywood.
Photo gallery - Robert Pattinson and Kristen Stewart through the years: