Barack Obama offers condolences to Nelson Mandela's widow in call

President Barack Obama spoke to Nelson Mandela's widow, Graca Machel, by phone on Friday to express condolences over the former South African president's death, the White House said.

"The president thanked Mrs Machel for the profound influence that Nelson Mandela has had on him, and underscored the power of President Mandela's example for the people of South Africa and the entire world," the White House said in a statement.

"President Obama expressed gratitude and thanks for the joy that Graca Machel brought to Nelson Mandela's life, and the commitment to a peaceful, fair, and loving world that she and President Mandela shared."