JOHANNESBURG (AP) - Ahmed Kathrada, a warhorse of the anti-apartheid struggle, was allowed just a few minutes at the hospital bedside of his critically ill comrade, Nelson Mandela. It was, he said, a traumatic experience to see the former president, physically robust during their prison years together, in such a fragile state.

Mandela could not speak but his face "changed" and he recognized his visitor "through his eyes," Kathrada said of the July 1 encounter, which was overseen protectively by Mandela's wife, Graca Machel.

This is the image of Mandela that South Africans, and many people around the world, find hard to accept. The man who withstood 27 years in jail and led his country from conflict toward reconciliation, is as vulnerable as anyone his age, and monitored around the clock by doctors.

The 94-year-old was admitted to a Pretoria hospital on June 8 for a lung infection. The government said Thursday he is in critical but stable condition, and responding to treatment. Legal filings by Mandela's family have said he is on life support.

"All the years that we knew him, we knew him, somebody who was very conscious of his health, somebody who exercised in and outside of jail, regularly, and here you see a person who's different. A shell of himself," Kathrada, 83, said in an interview Wednesday with The Associated Press.

"It was an overwhelming feeling of sadness, and of course the unrealistic wish and prayer that he can be with us for longer and longer," said Kathrada, who joined Mandela in pivotal events of the early campaign against minority white rule. The two first met in 1946, before apartheid was even implemented.

Thursday marked the 50th anniversary of the 1963 raid on the Liliesleaf farm in Johannesburg that netted most leaders of the African National Congress, then a liberation movement and now South Africa's ruling party. Kathrada was among those arrested there, while Mandela was already in prison at that time.

Then followed the "Rivonia" trial at which Mandela, accused of sabotage and plotting to overthrow the government, declared that he was prepared to die, if necessary, for his belief in racial equality. He, Kathrada and others were sentenced to life in prison and sent to Robben Island, near Cape Town.

"He was a boxer, he was a gymnast, he was a very strong person," Kathrada, a member of parliament after apartheid, said of Mandela. "In prison too, when we were working at the quarry with pick and shovels, we found difficulty... but he was strong enough to adjust to that quickly."

He described Machel as a gatekeeper who makes sure visitors, including relatives, old friends and President Jacob Zuma, don't stay too long during trips to see her frail spouse. Her first husband, Mozambican President Samora Machel, died in a plane crash in 1986.

Human rights lawyer George Bizos, a member of the legal team that defended Mandela and others at the Rivonia trial, said Machel invited him to see Mandela in the hospital last month. The visit was canceled when the health of his friend deteriorated.

"None of us are immortal, but I can't really come to terms that he may pass away in the near future," Bizos said in a telephone interview.

He recalled a visit to Mandela in Johannesburg a week before the hospitalization at which the two men, along with Machel, chatted about "many things" for more than half an hour, including talk of their days together as law students in Johannesburg.

"He would ask me, 'Do you remember 'so-and-so,' is he still around? When did you last see him?'" Bizos said. Mandela sometimes repeated questions, like many elderly people whose minds are no longer sharp.

"They may not remember what they said 10 minutes before, but they remember what happened 50 years ago," he said.

Yet Mandela still had caring instincts. Bizos had left his jacket in his car, but Mandela thought he had taken it off in the house.

"'George, don't leave your jacket behind,'" he fondly instructed Bizos on that South African winter's day.

Memories pervade Kathrada's apartment in Johannesburg, where a framed prison dish hangs on the wall. It was a birthday gift in 1999 from Mandela, whose inscription reads: "To Kathy, Best wishes to a remarkable comrade."

A large photograph of the two men hangs in the foyer. Both are smiling broadly, and Mandela has his hand on Kathrada's knee.

Prior to last week's visit, Kathrada last saw Mandela in September in his rural home in Eastern Cape province, shortly before the former president was moved to the Pretoria-Johannesburg area for the first in a series of hospital stays.

Kathrada brought an album of photographs from Kazakhstan, where he had traveled for events held to honor Mandela's ideals on July 18, the beloved figure's birthday. The photographs showed children who had drawn images of Mandela or the South African flag with crayons on the ground.

"We went for lunch, while he stayed," Kathrada said. "And when we came back from lunch, he was still paging through this album."

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(Photo: STEPHANE DE SAKUTIN/AFP/GettyImages)