|Karzai has said that foreign forces need to remain in
Afghanistan for some time to come [GALLO/GETTY]
Despite the presence of 50,000 Nato soldiers, Afghanistan is struggling to emerge from years of conflict and instability.
Some 90 per cent of the world's heroin is still produced there, corruption is rife and the Taliban have regrouped.
The Afghan government faces the daunting challenge of reversing these trends and forging national unity.
Hamid Karzai, Afghanistan's president, was in France this week to boost aid donations.
Karzai had won a five-year term in Afghanistan's first direct presidential elections in October 2004.
President Karzai spoke exclusively to Sir David in Paris. He says Afghanistan will eventually wipe out heroin production in the country with the help of other nations.
|Tutu calls for international intervention
in Zimbabwe [GALLO/GETTY]
Archbishop Desmond Tutu rose to prominence in the 1980's as an opponent of apartheid. Since then, he has spoken out on a number of foreign issues.
He joins the show to discuss the crisis in Zimbabwe, a country marred by spiralling inflation, desperate food shortages and political violence ahead of a presidential run-off election due to take place in two weeks.
Thabo Mbeki, the South African president, has been criticised for his apparent inaction in his role as the chief mediator in Zimbabwe's political crisis and Tutu suggests that Kofi Annan, the former UN secretary-general, should take on the role of mediator.
He also calls for international intervention and says a peace keeping force should have been sent to Zimbabwe a long time ago.
|The popular author reveals how Alzheimer's
is affecting his life and work [GALLO/GETTY]
Terry Pratchett is one of the world's most popular authors.
The British writer is best known for the highly successful Discworld series of comic fantasy novels.
He has sold almost 60 million books worldwide, with translations into 33 languages.
Last year, he was diagnosed with Alzheimer's disease.
Rather than shy away from publicly discussing his condition, Pratchett has faced it with typical candour and humour.
Pratchett talks to Sir David about the disease, how it is affecting his work and how he has changed his lifestyle accordingly.
He says his typing and spelling is not as good as it used to be but that he has no trouble developing stories.
|Pilot represents the town of Dausa where
20 Gujjars were killed
In India at least 35 people have died in violence following protests by the Gujar community about their status in the caste system.
Thousands of soldiers and policemen have been deployed to quell the violence in the northern state of Rajasthan.
The Gujjar community are classified by the government as OBCs, or Other Backward Class.
However, the Gujjars, who fall somewhere in the middle of the Hindu caste hierarchy, want to be relegated to one of the lowest castes who, as part of the government's affirmative action policy, can gain access to better jobs and education.
While the Hindu caste system has been officially abolished in India, it remains a powerful influence.
Sir David is joined by Sachin Pilot, a member of the Indian parliament for the town of Dausa where 20 Gujjars have already been killed.
Pilot says that while violence has ceased, the situation is still precarious and he criticises the police for opening fire on protesters.
This episode of Frost over the World aired on Friday, June 13, 2008
Frost over the World airs at 18:00GMT every Friday on Al Jazeera English and is repeated during the week.