White House spokesman Marlin Fitzwater said the rebel assault, on Nicaragua’s remote gold and silver mining district, was “very encouraging.”When asked if the military action was appropriate at a time when high level representatives of the Contras and the leftist Sandinista regime were in Santo Domingo for indirect negotiations over a cease fire in the six year old civil war, Fitzwater replied: “Absolutely. The purpose of the resistance, from our point of view, is to keep pressure on the Sandinistas…