Fresh red meat is also strongly linked to cancer and the WHO is expected to categorise it one level below processed meat, as "probably carcinogenic".
But it also provides many nutritional benefits and is high in protein, iron and vitamin B12, which prevent tiredness and infections.
Dr Rachel Thompson, of the World Cancer Research Fund UK, said: "If people can avoid it [processed meat], they should. It's better to get what you need from fresh red meat.
"Processed meat contains more salt and fat and there is likely to be a higher cancer risk from the actual processing."
She added: "If there's someone who has a bacon sandwich every morning and a ham sandwich for lunch, they are at higher risk. They should really try to cut down."
Government guidelines introduced in 2011 recommend that adults eat no more than 70g of red or processed meat each day - equivalent to one small sausage or two rashers of bacon a day or one lamb chop every other day.
A spokesman for Public Health England, the government agency for preventing illness, said it would "consider" the WHO's guidelines as soon as they come out.
A four-year study of 500,000 middle-aged men and women, by Oxford academics, found those who ate red or processed meat four or more times a week were 42 per cent more likely to develop bowel cancer than those who had it less than once a week. The research will be presented to the National Cancer Research Institute in Liverpool next month.
Experts think the chemical haem in red and processed meat damages the DNA of cells in the digestive system, triggering cancer. Surveys show four in ten men and one in ten women eat more than 90g of red or processed meat a day. The impending WHO announcement has caused alarm in the meat industry.
Barry Carpenter, of the North American Meat Institute, pointed out that almost every substance is deemed to pose some sort of cancer risk. "Scientific evidence shows cancer is a complex disease not caused by single foods and that a balanced diet and healthy lifestyle choices are essential to good health," he added.
Cancer Research UK's Casey Dunlop said: "The link between red and processed meat and certain types of cancer ... has been building for decades ... supported by a lot of careful research."
- Daily Mail