The Collaborative International Dictionary of English v.0.48:

Pelletise \Pel"let*ise\, Pelletize
\Pel"let*ize\(p[e^]l"l[e^]t*[imac]z), v. t.
   To form into small balls; as, to pelletize ore. The spelling
   pelletise is mostly British.
   [PJC]