A race to the South Pole involving Britain's Prince Harry and teams of injured troops has been cancelled due to safety concerns, organisers said Saturday, but the veterans will trek on together to the globe's most southerly point.

The Walking With The Wounded charity said that five days into the gruelling trek, "it became obvious that underneath the concrete determination of all the team members, the harsh reality of the Antarctic was starting to take its toll".

The three teams, made up of wounded veterans from Britain, the United States and the Commonwealth (represented by Canada and Australia), will trek the final 112 kilometres (70 miles) together and aim to arrive by next Friday or Saturday, the charity said.

Harry, the 29-year-old fourth-in-line to the throne, is a helicopter gunner with the British army and patron of Walking With The Wounded. He had been trekking with the British team.

The charity's expedition director Ed Parker said the teams had been progressing well but the "unprecedented terrain" had placed a lot of stress on the wounded veterans, who include seven amputees.

"With careful consultation from our doctor and race team, we have put the race on hold," Parker said.

"This does not mean that the expedition is over. Far from it. We came down here, determined to get 12 men and women, all injured in conflict, to the South Pole, and so we will."

He added: "By Friday or Saturday next week, I strongly believe that every member of the expedition will be standing on the South Pole, celebrating what will have been the most extraordinary shared journey."

The veterans are enduring temperatures as low as minus 35 degrees Celsius (minus 31 degrees Fahrenheit) and wind speeds of around 50 miles (80 kilometres) per hour.

They are pulling 70-kilogram (155-pound) sleds throughout the 335-kilometre race.

Walking With The Wounded raises funds to retrain injured troops and help them find new careers outside the military.

Launching the race at London's Trafalgar Square last month, Harry described the trek as "a wonderful display of courage" by the troops.

"These guys aim to achieve something quite remarkable, and in doing so will prove to everybody else that even though you've lost a leg or lost an arm, or whatever your illness may be, that you can achieve pretty much anything if you put your mind to it," he said.

Harry joined the charity for part of a trek to the North Pole in 2011, but had to come home early to be best man at his brother Prince William's wedding.