Defying terminal cancer, President Jose Napoleon Duarte returned from Washington to begin catching up on official business after six weeks' absence.

"I am here now to reassume the presidency, in order to continue working for what I most love: democracy," the 62-year-old Duarte said upon arriving Monday from the U.S. capital, where he underwent diagnosis and treatment beginning May 31."I certainly am not cured. But I am strong. I have the capacity and the strength to carry out both the medical requisites my disease demands and my work for the people," said Duarte, the Western Hemisphere' staunchest U.S. ally.

Duarte, whose five-year term ends June 1, 1989, was leaner than when he left and his face was drawn.

But his step was firm and his embrace appeared strong as he greeted Rodolfo Castillo Claramount, the vice president and acting chief executive, and other officials on the tarmac of Ilopango Airport outside the capital.