President Obama today expressed concern for Nelson Mandela's health, but said the anti-apartheid leader is "as strong physically as he's been in character and in leadership over so many decades."

"Obviously we're all deeply concerned with Nelson Mandela's health. He's a hero, I think, to all of us," Obama told reporters. "We will be keeping him in our thoughts and prayers and his entire family."

The former South African president has been hospitalized for a recurring lung infection but is "responding positively" to treatment, according to the South African president's office.

"Hopefully he will come out of this latest challenge," Obama said.

"We all recognize that he has given everything to his people, the people of South Africa, to the people of the continent, and he's ended up being an inspiration to all of us," Obama said. "When you think of a single individual that embodies the kind of leadership qualities that I think we all aspire to, the first name that comes up is Nelson Mandela. And so we wish him all the very best."

The president's comments came as he met with the leaders of Sierra Leone, Senegal, Malawi and Cape Verde at the White House.