The Clinton administration and international donor organizations, heeding a warning from four Central American presidents that the ravages of Hurricane Mitch are endangering democracy in their countries, pledged more than $1 billion Thursday in relief and interest-free loans to the devastated region. “You are our neighbors, our friends, our partners,” Undersecretary of State Stuart E. Eizenstat said during an emergency meeting of the visiting presidents and a group of donor organizations. “When you suffer, we suffer. When you hurt, we hurt with you. When you need help, we are there to help.” It was not clear, however, whether the promises of aid would match the enormous need. Describing the extent of the horror six weeks ago, President Carlos Flores of Honduras said Thursday that the storm “destroyed 50 years of efforts to build an infrastructure and stole away assets of two generations of Hondurans...”