"The flaw that took place in Afghanistan was preventable," the dismissed diplomat, Peter Galbraith, said Monday on ABC's "Good Morning America."
Galbraith said the United Nations "did not exercise its responsiblity." In dismissing Galbraith, the deputy envoy at the U.N. mission there, Secretary-General Ki-moon did not specify the nature of their differences.
Galbraith said the argument was over how the U.N. should have handled the delicate situation.
Preliminary results from the Aug. 20 election show President Hamid Karzai won a majority, with former foreign minister Abdullah Abdullah in second place. But proclamation of a winner has been delayed pending a partial recount by the U.N.-backed Electoral Complaints Commission (ECC).
Interviewed following the deadliest attack on American troops in a year, Galbraith said he doesn't think this is the right time to bring on an Iraq-like surge in the wartorn country.
"It makes no sense to ramp up," he said. "On the other hand, we cannot afford to pull out."
The Obama administration is weighing whether to send thousands of additional U.S. forces to Afghanistan, as commanding Gen. Stanley McChrystal reportedly has urged.
Galbraith also said that unless U.S. and coalition troops can secure significant population centers in Afghanistan, "we're going to be there as an occupying force for a long time ... and that doesn't make any sense."
(This version CORRECTS ADDS 4 grafs to UPDATE with addl quotes; SUBS 5th graf to correct spelling of Karzai's first name.)