WDTCN disable

Hello,
I have a AT89C5131 development kit and I want do disable the WDTCN (watchdog timer) but in the list of the registers in the file "at89c5131.h" it looks like there are two registers:
Sfr ( WDTRST, 0xA6 ) ;
Sfr ( WDTPRG, 0xA7 ) ;

What do I need to do in order to Disable the watchdog timer.

Thanks!