The organisation, run entirely by 15 volunteer co-ordinators, has already helped around 1,500 letter-writers to befriend US death- row prisoners since its launch in 2000.
Marco Ardimento, who quit his own marketing agency AMT Partnership last November, is devoting the next two months to the campaign by contacting 100 voluntary organisations already involved in humanitarian and justice issues.
There are around 3,700 people on death row in the US, and Human Writes estimates that more than half do not receive any correspondence. It says these prisoners will wait up to 25 years to be executed, while living in cramped conditions with little daylight and poor food. Sensory deprivation is common.
Ardimento will contact organisations such as Amnesty International, the Howard League and the WRVS. He wants them to provide him with a platform to alert staff and volunteers to the need for penfriends and to extol the benefits of befriending such people.
He said many death-row inmates are disowned by their families, who feel stigmatised through association with them. Many penfriends are afraid to admit they write to murderers.
"But, I'm proud of writing and receiving the letters and want to get across the enormous, uplifting benefits," Ardimento said. "They represent normal and unconditional friendships, notwithstanding the 5,000 miles and a high security prison between penfriends."
He added: "I plan to ensure that by 7 June, everyone on death row who has expressed a desire to have a penfriend, has one. Once we have achieved that, I am convinced that prisoners will spread the word that they can get a penfriend if they ask for one."