OK: Robert tells Kristen to Choose.

According to the latest issue of OK Magazine, Robert Pattinson told Kristen Stewart that she needs to choose between him and her longtime boyfriend, Michael Angarano. I know who I would choose...just sayin...

"Clearly, somethings got to give – and insiders tell OK! that "Edward" has handed his "Bella" an ultimatum: Make up your mind, or drive a stake through it; we're done.

"Robert is completely frustrated. If Kristen isn't interested in a serious relationship, she needs to tell him so he can move on," says one source, adding that R-Patts, 23, is giving 19-year-old Kristen a couple months to sort things out while he's in NYC filming Remember Me, an indie flick about star-crossed lovers (production begins June 15).

The actor wants a resolution by the time he and Kristen reunite in Vancouver this fall to shoot Eclipse.

"He's asked her to choose between him and Michael this summer," says the source. "Robert's not willing to be strung along."

Read it all at OK Magazine online.