Adding to the fun:

*--- SAS/OR ---;
proc nlp data=circle;
parms x0 = 0, y0 = 0, R = 1;
bounds R >= 0;
delta = ( (x - x0)**2 + (y - y0)**2 - R**2 ) **2;
min delta ;
run;

*--- SAS/STAT ---;
proc nlin data=circle converge=1e-6;
parms x0 = 0, y0 = 0, R = 1;
bounds R >= 0;
delta = ( (x - x0)**2 + (y - y0)**2 - R**2 ) **2;
model zero = delta;
run;

zero is a column of 0's to satisfy nlin syntax. Cheers.