BBC News with Jonathan Weekley.

The Argentine government has withdrawn a tax increase on grain exports, a day after the Senate rejected the measure following months of protests. The decision is a blow to President Cristina Fernandez de Kirchner. As Daniel Schweimler reports from Buenos Aires.

This is the first step backwards the Argentine government that has to take since their export tax increases were announced in March. The President Cristina Fernandez de Kirchner had little choice after suffering a dramatic setback when the issue was defeated after an 18-hour-long debate in the Upper House of Parliament earlier this week. Argentina's farmers have won a major victory that the government says it needs the money to tackle poverty, and it believes the farmers whose soaring grains fetch high prices on world markets can afford to pay.

In an effort to reduce its dependence on costly food imports, the Cuban President Raul Castro has agreed to lend vacant state lands to private farmers and cooperatives. Michael Voss now reports from Havana.

Raul Castro considers reducing costly food imports as a matter of national security, increasing agricultural production is seen as a key priority which justifies transferring land from state-controlled farms into more efficient private hands. In a presidential decree published in the Communist Party newspaper, Granma, the Cuban leader announced that private farmers who had shown themselves to be productive can get up to 40 hectares of land on renewable 10-25 year leases. Accepting a wide range of limited role for private enterprise is one of the most significant Raul Castro's reforms to date.

The army in Mexico has seized at least 12 tons of marijuana in the border city of Tijuana, the single biggest seizure of the drugs since thousands of troops were sent to the western border region to tackle trafficking. Officials say about three tons of the drugs were found in a stolen car on Thursday while the remainder was discovered on Friday. President Felipe Calderon came to power last year promising to rid Mexico of drug-related crime.

In the face of international pressure, the South African President Thabo Mbeki has allowed the African Union and the United Nations to join his mediation efforts in Zimbabwe. Mr. Mbeki will remain the main mediator between the Zimbabwean government and opposition, but he has agreed to consult regularly a new reference group, including the AU and UN. This report from Grant Ferrett.

The new broadened mediation effort in Zimbabwe was announced in Pretoria after a talk between President Mbeki and the head of the African Union and an UN envoy. The South African government presented it as an endorsement to Mr. Mbeki's efforts over the past year. But he'll no longer be able to act alone, and will now have to liaise with his AU and UN colleagues. The announcement was welcomed by Zimbabwe's opposition which had complained that Mr. Mbeki was biased in favor of President Robert Mugabe.

World News from the BBC.

World leaders have been congratulating Nelson Mandela as he marked his 90th birthday at his rural home state in South Africa. President Bush praised his leadership as an example of courage, hope and the power of freedom. Asked if he had a message for the world, Mr. Mandela called on the rich to share their wealth with the poor.

There are many people in South Africa who are rich, who can share those riches with people who are not so fortunate, who have not been able to conquer poverty, if you look around, even in towns, not only in the countryside, even in towns, there's a lot of poverty.

A giant crane has collapsed at an oil refinery in the American City of Houston, killing four people and injuring at least six others. Television pictures showed the crane, which was several hundred meters long, appearing to break off the base. Officials are investigating the cause of the accident.

Two French aid workers have been kidnapped in central Afghanistan. The organization Action Against Hunger said its workers were abducted while they were sleeping by an armed group which tied up their guards before breaking into their house. It added that the operations had been suspended. The French Foreign Ministry said a crisis center had been set up to handle the case.

The South African athlete, a double-amputee Oscar Pistorius has failed to be selected to compete against able-bodied runners at the Olympic Games in Beijing. Pistorius missed the Olympic qualifying time for the 400 meters in his last race, and the South African Athletes Board has left him out of its relay team as well. It said four other South Africans have faster times. Pistorius was initially banned on the grounds that his carbon-fiber artificial legs give him an unfair advantage, but that ruling was overturned.

BBC News.