Justin Timberlake might want to hold off on that marriage proposal – at least until he and Jessica Biel work through their jealousy issues.

Jessica, 26, blew a gasket after hearing about the heat Justin, 27, generated with sultry 20-year-old singer Rihanna while filming the music video for her single "Rehab" in the California desert recently, sources say.

"Jessica wasn’t there, but she heard about it, and everyone was gushing about the intense chemistry between Rihanna and Justin," an insider revealed. "That’s not the kind of news a girl who’s waiting on a proposal wants to hear, and she was fuming.

"Jessica also saw pictures from the video set while online and felt sick to her stomach when she saw Rihanna in her skimpy outfits looking incredibly sexy!"

The Stealth thesp’s been telling pals she intends to be not only married, but  pregnant by next summer.

But both Justin and Jessica suffer from bad cases of jealousy that could derail their nups, said the source.

Justin wasn’t happy to hear about the sultry sex scenes his girlfriend of nearly two years shares with Ben Barnes in her upcoming film Easy Virtue, and made several trips to England where they were shooting, said the source.

"Justin was put off by how chummy Jess and Ben seemed," says the source. "And while Jess read Justin the riot act after she heard that he was ogling Rihanna’s behind between takes, Justin swore up and down that the video shoot was all business.

"Those two are a good match – but they both are so possessive."