By Philip Pullella ABOARD THE PAPAL PLANE (Reuters) - Pope Francis acknowledged on Monday he had neglected problems of the middle class and said he was willing to have a dialogue with Americans who disagree with his criticism of capitalism. Francis, speaking to reporters on the papal plane returning from a gruelling 8-day trip to Ecuador, Bolivia and Paraguay, also said he hoped the Greek crisis could lead to more oversight so other countries would not experience the same problems. During the hour-long conversation with the Francis, who has made defence of the poor a major plank of his papacy, a reporter asked why he had hardly ever spoken about the problems of the "working, tax-paying" middle class.