President Barack Obama and Cuban President Raul Castro shook hands on Friday at a summit in Panama, a symbolically charged gesture as the pair seek to restore ties between two Cold War foes.
"At the Summit of the Americas this evening, President Obama and President Castro greeted each other and shook hands," said Bernadette Meehan, National Security Council Spokesperson.
A White House official said however the pair did not have a substantive conversation. The two are expected to meet on Saturday.
US President Barack Obama has already spoken with Cuban President Raul Castro ahead of their symbolic meeting in Panama.
A Cuban official confirmed the two leaders shared a phone call on Wednesday as the countries work to mend once bitter Cold War relations.
Mr Obama and Mr Castro, who have only previously met briefly and informally, will share the same stage with other leaders at a regional summit in Panama later today.
It is the first time a US president has held a formal meeting with a Cuban leader since Mr Castro's older brother Fidel Castro toppled US-backed dictator Fulgencio Batista in a 1959 revolution.
In response to the historic handshake between Barack Obama and Cuban president Raul Castro, the US National Security Council has said: "This wasn't a pre-planned encounter. Above all else, today is about honouring Nelson Mandela and that was the President's singular focus at the memorial service.
"We appreciate that people from all over the world are participating in this ceremony."
President Raul Castro says Nelson Mandela set an "insurmountable example" to Latin America and the Caribbean which he says are "currently moving towards unity and integration for the benefits of their peoples on the basis of respect for diversity".
Cuban President Raul Castro is speaking at the memorial service for Nelson Mandela.
He described Mandela as the "ultimate symbol of dignity and unwavering dedication to the revolutionary struggle for freedom and justice".
US President Barack Obama shook hands with his Cuban counterpart Raul Castro at the memorial service . He is due to address the stadium shortly.
US President Barack Obama will lead tributes from world leaders to Nelson Mandela tomorrow at the memorial service in Johannesburg.
UN Secretary General Ban Ki-moon will lead the international tributes, followed by Dr Nkosazana Dlamini Zuma from the African Union.
Obama will be followed by Brazil's President Dilma Rousseff, China's Vice-President Li Yuanchao, Namibia's President Hifikepunye Pohamba, India's President Pranab Mukherjee and the last international tribute will come from President Raul Castro.
In a surprise move, Cuba's new parliament has named a rising young star as Raul Castro's first vice president.
Miguel Diaz-Canel, 52, a member of the political bureau who rose through the party ranks in the provinces to become the most visible possible successor to Castro.
Diaz-Canel would succeed Castro if the 81-year-old cannot serve his full term.
Cuba's President Raul Castro has announced that he will stand down from office in 2018 bringing to an end almost 60 years of rule under the family dynasty.
Raul took over from his brother Fidel Castro in 2008, but has spoken about limiting the number of terms for senior government officials including the presidency.
Castro made the announcement in a nationally broadcast speech shortly after the Cuban National Assembly elected him to a second five-year term in the opening session of the new parliament.
He starts his second term immediately. In 2018, Castro will be 86.
The Cuban President Raul Casto says he will retire at the end of his next term.
He has just been sworn in for his second term as President which will expire in five years.