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Secret Service agents assigned to protect four U.S. presidents at Tuesday's memorial service for Nelson Mandela are facing a potential clash of egos that could translate into a security nightmare.

Former Secret Service agent Dan Bongino, who protected Presidents George W. Bush and Obama, told FoxNews.com the real test at the South African memorial site will lie in how well the agents will be able to navigate an ego-heavy political minefield.

“The security part is easy,” Bongino said. “The politics of security is what makes it a nightmare. And the egos.”

“With a state funeral, you’re dealing with numerous heads of state and they all have egos,” he said. “In addition, you’re dealing with the tragedy of the situation. You can’t go in randomly shaking down mourners.”

Bongino, author of “Life Inside the Bubble: Why a Top-Ranked Secret Service Agent Walked Away from It All," adds,"every head of state wants his entire team in there with their weapons.”

Obama and his wife, Michelle, left Washington Monday for South Africa on Air Force One.

The president, who was scheduled to speak at the memorial service for the anti-apartheid icon, was joined on board by former President George W. Bush and former Secretary of State Hillary Clinton. Former Presidents Bill Clinton and Jimmy Carter will join the group in Johannesburg.

Nearly 100 heads of state are expected to gather at the 94,000-capacity FNB Stadium Tuesday. It is the same site where Mandela made his last public appearance, and also the location for the 2010 World Cup closing ceremony.

Many experts have questioned whether South Africa will be able to rise to the security challenge posed by having so many world leaders in one location.

Rory Steyn, head of Mandela’s security, told The Associated Press that the event would be the biggest the country has seen.

“It’s unprecedented,” he said.

Steyn, who now runs a private security firm in South Africa that will provide protection for 25 dignitaries this week, says the massive scope would be a challenge to any country.

South Africa’s Defense Minister Nosivewe Mapisa-Nqakula told the media that more than 11,000 troops have been deployed, as well as a coordinated plan involving the military, air force and police.

"Thousands" of officers will direct traffic, protect mourners and help the bodyguards of visiting dignitaries, Lt. Gen. Solomon Makgale, a spokesman for the South African Police Service, told the AP.

"We will be on hand to make sure people are able to grieve in a safe environment," Makgale said.

Multiple media outlets were reporting Monday that Sidas Security, a private South African security firm, was still trying to hire ahead of Tuesday’s event. The firm plans to have more than 1,500 guards in place Tuesday.

Workers were also seen late Monday constructing a stage at the stadium, where South African President Jacob Zuma is scheduled to give the keynote address.

Also slated to speak at the four-hour service are U.N. Secretary-General Ban Ki-moon, Brazilian President Dilma Rousseff, Indian President Pranab Mukherjee; and Cuban President Raul Castro.

The security challenges in South Africa are as daunting as they were for the funeral of slain Egyptian president Anwar el-Sadat in October 1981. Within four days of Sadat’s assassination, thousands of soldiers, airmen and special security agents were on call to make sure the leaders of more than 80 countries attending the funeral would be safe. Pictures of policemen and soldiers carrying automatic weapons and lining the streets were a constant reminder of the safety issues.

The American delegation – which included U.S. Presidents Carter, Ford and Nixon - was guarded by at least two dozen Secret Service agents, according to media reports.