Harare - Zimbabwe's government has hit back at Botswana's President Ian Khama following his comments asking President Robert Mugabe to step down.Khama, in an interview with Reuters news agency on Wednesday, said Mugabe should step aside without delay for the sake of Zimbabwe and the region, comments that "shocked" officials in Zimbabwe. "It is obvious that at his [Mugabe's] age and the state Zimbabwe is in, he's not really able to provide the leadership that could get it out of its predicament," Khama said.Economic collapse "They have got plenty of people there who have got good leadership qualities who could take over." Botswana is home to an estimated 100 000 Zimbabweans - a fraction of the three million believed to be in South Africa - although this is still enough to strain public services in a nation of 2.3 million people. It has felt the full effects of its neighbour's economic collapse under the weight of political violence and hyperinflation. Although Zimbabwe's economy stabilised in 2009 with the scrapping of the Zimbabwe dollar, a slump in commodity prices over the last two years has triggered a cash crunch, raising discontent in the country. Factions of Mugabe's ruling Zanu-PF party are locked in a bitter struggle to succeed the only leader Zimbabwe has known, but no clear potential successor has emerged.