Krasinski, best known for his role as Jim on NBC comedy The Office, has appeared in front of producers several times.  From Fox411:

"John has read 4 times and is doing screen tests," our source tells us.  "He has screen tested 2 times so far.  It's very likely that he will be the new Captain America.  He is a favorite among the key decision makers and has been asked to come back for more this week."

At this point, Krasinski is the main focus at Marvel.

"The big bosses are having him read with multiple actresses up for the female leads.  They want to lock down the role and then they will narrow down everyone else."

I really don't see Krasinski as a good fit for this part.  I like the guy and he's great in a comedic role, but I just can't see him as Captain America.  The Captain is supposed to stand up for America and justice and so forth, not be witty and make clever jokes all the time.  I mean just look at that picture, doesn't exactly scream super hero.  I'm not alone in this opinion either.  From one of the Marvel workers interviewed by Fox:  "It's a surprise and we are bracing ourselves for 'that guy from 'The Office'' to land Captain America.  They are not really looking at the other guys, so it's time to get ready to work with him."

That's a sign of disapproval without wanting to risk losing his job for blasting them on this questionable decision.  Stay tuned for when they make the final announcement, sometime in the near future.  The First Avenger: Captain America is set for a July 22, 2011 release.