BEIJING, May 16 -- Jake Gyllenhaal is planning to propose to Reese Witherspoon. The couple -- who met on the set of "Rendition" last year -- have discussed marriage and are ready to cement their relationship.

    A source said: "They've been talking marriage for a while. They'll be formally engaged any day now. They want to spend the rest of their lives together." Reese, who has two children with her ex-husband Ryan Phillippe, wants to tie the knot before she moves in with Jake.

U.S. actors Jake Gyllenhaal (R) and Reese Witherspoon attend a photo call to present their latest movie 'Rendition' at the Rome International Film Festival October 21, 2007.

A friend of Reese revealed to America's OK! magazine: "This is a very serious relationship. But Reese is very conservative and traditional. I'm sure she doesn't want her kids to see her 'living in sin'."

    The couple -- who reportedly plan to set up home in a $6 million California ranch -- looked smitten with each other as they dined at the Hominy Grill in South Carolina recently.

    Restaurant manager Brandy Mangum said: "They couldn't keep their eyes off each other. The entire time, he was so attentive.

    It was really sweet. They really do make the perfect couple." Jake's spokesperson has denied the actor is planning to wed the Oscar-winning star.