svyglm fit method?

Dear list,
I am using svyglm in the survey library to fit a binomial logistic  
regression accounting for sample design.  The documentation says the  
models are not fit by maximum likelihood, so my question is what is  
the fitting method?  Pseudo likelihood?  Generalized least squares?   
Thanks for any insight.
Best,
Corey

Corey Sparks
Assistant Professor
Department of Demography and Organization Studies
University of Texas at San Antonio
One UTSA Circle
San Antonio, TX 78249
210 458 6858
corey.sparks at utsa.edu