Mandela and de Klerk jointly won the Nobel Peace Prize in 1993 for their efforts to end apartheid.
Back at home, Thatcher was a highly polarizing figure in British politics.
Police are stepping up security ahead of the funeral, amid concerns that protesters angered by Thatcher's actions in office may take to the streets.
Many Britons blame her for creating soaring unemployment, when she reduced or eliminated many government subsidies to businesses and took on unions. Her battle with striking coal miners won her few friends in mining communities in northern England and Wales.
But supporters believe the tough reforms she pushed through transformed the British economy and gave many working people new freedoms.
London's Metropolitan Police, the City of London Police, who cover the city's financial district, and the British Transport Police are working together "to ensure that events that day pass off safely," a statement said.
Police officers will be deployed along the route, with other mobile groups ready to be deployed to any outbreaks of trouble, the Met Police said.
The force has urged anyone planning protests to let police know ahead of time.
"There has been much speculation about what levels of protest may take place. I would ask anyone who wishes to demonstrate then, or in the coming days, to come and talk to us," Commander Christine Jones said.
"The right to protest is one that must be upheld. However, we will work to do that whilst balancing the rights of those who wish to pay their respects and those who wish to travel about London as usual."
Police will implement a range of security measures in line with the current threat level, Jones said.
London's Evening Standard newspaper reported Wednesday that anarchists are planning to stage a mass "party" Saturday in Trafalgar Square to celebrate Thatcher's death.
Ian Bone, founder of the Class War group, is quoted by the newspaper as saying thousands of anti-Thatcher protesters will gather from across the country for the event. They'll include miners and steel workers scarred by her battle with the unions, he said.
Trafalgar Square, in the heart of London, was the scene of violent rioting in 1990 against a hugely unpopular tax brought in by Thatcher. The so-called poll tax was levied on community residents rather than property.
A post on what appears to be Bone's blog also calls on people to attend the "Class War Party" in Trafalgar Square. "Best night out since the poll tax riot," it promises.