President Barack Obama heads to Africa on a long awaited first major tour on Wednesday, but a trip meant to make up for lost time is instead being overshadowed by Nelson Mandela's fading health.
Obama will leave Andrews Air Force base outside Washington for a weeklong trip that is scheduled to include stops in Senegal, South Africa and Tanzania.
Yet Mandela's fragile state of health has sparked speculation that the tour could be halted, or radically changed, if the anti-apartheid icon passes away in the hours before Obama leaves, or while he is on the continent.
The White House has said that it will defer to Mandela's family on whether the president would visit his ailing 94-year-old political hero in the Pretoria hospital where he has been for nearly three weeks.
South Africa's foreign minister Maite Nkoane Mashebane said that while Obama would have loved to see Mandela, a meeting with the former South African leader would be impossible as he was "indisposed".
The men met in 2005, when the former South African president was in Washington, and Obama was a newly elected senator, and the two have spoken several times since on the telephone.
But there have been no face-to-face meetings between the first black presidents of the United States and South Africa since Obama was elected in 2008.
The White House sees Obama's visit as a chance to make up for lost time, as the president was unable to fit in a visit to sub Saharan Africa in his first term, apart for a brief stop in Ghana.
There has also been disappointment on the continent, after Obama's election as the first black US president in 2009 caused euphoria.
Obama hardly dampened expectations, declaring in a quick stop in Ghana in 2009: "I have the blood of Africa within me, and my family's own story encompasses both the tragedies and triumphs of the larger African story."
But Africa policy has languished, with Obama battling economic tumult, rebalancing US attention to a rising Asia, being outpaced by revolution in the Middle East and consumed by his legacy project of ending US wars abroad.
US officials are aware that emerging economic opportunities and energy resources in Africa have attracted a clutch of interest from rising rivals.
Washington noticed that new Chinese President Xi Jinping professed a "sincere friendship" with Africa when he visited the continent on his first foreign tour.
There is one glaring missing stop on Obama's itinerary: Kenya, the homeland of his late father.
In an unusual intervention in a foreign election, Obama in February urged the people of Kenya to avoid a repeat of violence that killed more than 1,000 people after 2007 polls.
That violence led to the indictment of Kenyan President Uhuru Kenyatta at the International Criminal Court in the Hague, making it politically impossible for Obama to pay an evocative trip to Kenya on this tour.
The president will stop first in Senegal, where he will meet President Macky Sall and pay an emotive visit to Goree Island and a museum and memorial to Africans caught up in the slave trade.
Then he will move onto Johannesburg, South Africa, on June 29, and the next day will hold talks and a press conference with President Jacob Zuma in Pretoria.
Later, Obama will hold a town hall meeting with young Africans at the Soweto campus of the University of Johannesburg.
On June 30, Obama will move onto Cape Town where his events include a visit to Mandela's jail cell on Robben Island and a roundtable with business leaders which will include senior members of the president's economic team.
The final leg of Obama's journey will take him to Tanzania, where his program includes talks and a press conference with President Jakaya Kikwete and a visit to the Ubungo power plant.
Obama will also lay a wreath at a memorial to 11 people killed in the US embassy bombing in 1998.