In Age of Ultron, there's a scene where the various team members try and fail to lift Thor's hammer. When Cap tries, he actually manages to budge it very briefly, and we see both him and Thor react as they notice. But then he grabs the handle and grunts and strains and it doesn't move.
However, his "struggle" to lift the hammer looks horribly fake compared to the other teammates, and it seems to suggest that Cap realized that he could lift it, but then chose not to so as to not embarrass Thor in front of the team.
Is there any official reason to either believe or refute that interpretation?