Zimbabwe's 92-year-old President
 Robert Mugabe should step aside without delay and allow new leadership 
of a country whose political and economic implosion since 2000 is 
dragging down the whole of southern Africa, Botswana President Ian Khama
 said.
Despite his reputation as one of Africa's most outspoken 
figures, Khama's remarks are certain to raise hackles in Harare, where 
factions of Mugabe's ruling Zanu-PF party are locked in a bitter 
struggle to succeed the only leader Zimbabwe has known.
Asked by 
Reuters if Mugabe, who came to power after independence from Britain in 
1980, should accept the reality of his advancing years and retire, 
63-year-old Khama responded: "Without doubt. He should have done it 
years ago."
"They have got plenty of people there who have got 
good leadership qualities who could take over," Khama, the UK-born son 
of Botswana's first president, Seretse Khama, and his British wife, 
Ruth, continued.
"It is obvious that at his 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, in comments that 
breach an African diplomatic taboo banning criticism of fellow leaders.
Botswana,
 the world's largest producer of diamonds, shares 800 km (500 miles) of 
border with Zimbabwe and has felt the full effects of its neighbour's 
economic collapse under the weight of political violence and 
hyperinflation since 2000.
Although the economy established in 2009
 with the scrapping of the worthless Zimbabwe dollar, a slump in 
commodity prices over the last two years has triggered a cash crunch 
that has fed through into unprecedented public anger at Mugabe.
No clear potential successor has emerged from the destabilising factional fight to take over afterMugabe.
Khama
 said the instability was damaging Botswana's efforts to wean itself off
 mining - which accounts for 20 per cent of GDP and nearly 60 per cent 
of exports - by promoting itself as a regional logistics and services 
hub.
The unrest was also forcing more and more Zimbabweans to leave the country, he added.
Botswana
 is home only 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.
Botswana's jails held "significant numbers" of Zimbabweans, Khama said.
"It
 is a big concern," the British-trained former general said. "It is a 
problem for all of us in the region - and it is a burden. There's no 
doubt about that."
Resurrection man
In the 
latest controversy over his health, Mugabe left a summit of southern 
African leaders at the end of August without warning and went to Dubai, 
fuelling rumours he had been taken gravely ill or may even have died.
Khama
 did not discuss any specifics of Mugabe's condition at the meeting but 
said his counterpart looked tired. "We're talking about a 92-year-old 
man and there's just so much you can do at that age to try and keep up."
Mugabe
 frequently refers to himself as "fit as a fiddle" and hints at a desire
 to stay in power until he is 100. After his Dubai trip, which he 
attributed to a family matter, Mugabe joked about online reports of his 
imminent demise.
"Yes, I was dead. It's true I was dead. I 
resurrected as I always do. Once I get back to my country I am real," he
 told reporters at Harare airport.
Khama reiterated his 
government's concerns about the credibility of the elections Mugabe has 
won in recent years, but said irrespective of the results no leader 
should cling on to power for that long.
"My opinion has always 
been that 10 years leading any kind of organisation - not just a country
 or a government, any organisation - is pretty much the maximum," he 
said.
During its 50 years since independence, Botswana has emerged
 as a politically and economically stable nation that has used its 
mineral wealth prudently - a rarity on a continent where such treasures 
have been routinely squandered, stolen or the cause of civil war.
Khama's
 second five-year term in office ends in 2018 when he will hand over to 
vice-president Mokgweetsi Masisi in a carefully scripted political 
succession that makes instability almost impossible.
After 2018, 
Khama, a keen nature-lover whose wood-panelled office is adorned with 
pictures of the African savannah, said he wanted to dedicate his time to
 tourism and conservation.
Thanks to a focus on safari tourism and
 a zero-tolerance approach to poaching, Botswana boasts more than 
150,000 elephants, a third of Africa's entire population of the animals.
But
 Khama said there was no room for complacency in the fight against the 
illegal ivory trade given the rampant poaching in other countries on the
 continent.
"One day if their animals become extinct and we still have viable populations, all the guns will be focused on us," he said.