Ashton Kutcher and Mila Kunis
Jon Kopaloff/FilmMagic; Kristina Bumphrey/Startraks
04/26/2012 at 09:15 AM EDT
and Mila Kunis
are longtime friends – but are they friends with benefits?
Kunis tells Extra
in a new interview from CinemaCon, "A friend is a friend."
And the actress shoots down rumors that the two are dating, saying, "It's absurd."
Still, one source close to Kutcher says the former That '70s Show
costars – who just spent a cozy weekend together
in Carpinteria, Calif. – are enjoying spending time together, but not ready for a serious relationship.
"They're both single, having fun," the source tells PEOPLE. "There's nothing serious going on – just friends having fun."
It should be noted that both Kutcher, 34, and Kunis, 28, have some onscreen experience with relationships that morph between friendship, romance and more. Kunis costarred in Friends with Benefits
with Justin Timberlake
, while Kutcher appeared with Natalie Portman
in No Strings Attached
about a pair who have a physical relationship that turns more serious.
Another source told PEOPLE that Kutcher, who recently split
from Demi Moore
, "was so in love with [Mila] for a while when they worked together. ... It never happened, but I'm not surprised by this – at all."