Regarding the editorial President of the World Aug. 29: It is arrogant to consider the president of the United States to be "president of the world." In any case, our president does not seem suited for this role.A world president should be skilled in peacemaking; two wars have been fought by this administration plus continuing proxy wars in Central America. A world president should actively discourage a weapons trade that almost guarantees future wars; the US now leads the world in arms sales. A world president should care about all nations equally, and all the peoples of the world, especially the poor who form the vast majority; conditions for the poor in this country deteriorated during the 1980s and do not ap pear to be improving under this administration. Helen Ring, Wilton, N.H. Letters are welcome. Only a selection can be published, subject to condensation, and none acknowledged. Please address them to "Readers Write," One Norway St., Boston, MA 02115.