conversion - In ffmpeg, how to delay only the audio of a .mp4 video without converting the audio?

In my .mp4 file the audio delay is -3840 ms. I synced it in KMplayer, and I don't want to use MKVGUI to make a .mkv file. I just need to delay the audio by -3840 ms, everything else intact.
What would be the right command to accomplish this using ffmpeg?
I would appreciate your help.