How to change PAL display output to NTSC?

I'm trying to use my PAL PS3 with retroarch to play 60hz snes roms on a CRT. The CRT can display pal and ntsc but my PS3 only gives me PAL video output display options. As a result the roms play at 60hz while displaying at 50hz, which is causing some flickering.

Is it possible to change the display output to NTSC? Thanks.