Here is a way to disable sleeping when pressing the power button on 10.9.2. In Terminal, type in the following command and then press Enter.
defaults write com.apple.loginwindow PowerButtonSleepsSystem -bool no

This causes the ‘Are you sure you want to shut down your computer now?’ dialog to come up much quicker too.

[crarko adds: I tested this, and it works as described. I had to log out and log back in; I’m not sure if that’s necessary.]

Source: Mac OSX Hints