The mother of the US ambassador killed during the 2012 attack in Benghazi has pleaded with Republican presidential nominee Donald Trump to refrain from using her son's name during his election campaign.

"As Ambassador J. Christopher Stevens’s mother, I am writing to object to any mention of his name and death in Benghazi, Libya, by Donald Trump’s campaign and the Republican Party," Mary F. Commanday of Oakland, California, wrote in a letter to the New York Times which was published on Saturday.

Stevens, then the top US diplomat in Libya, was among four Americans killed in the Sept. 11, 2012, attack by militants against the Benghazi compound. The Trump campaign has frequently faulted Hillary Clinton, who was secretary of state at the time, for what they say was her failure to provide enough security to the outpost and for first saying the assault was the work of people angry at a crude YouTube film which mocked Islam.

"I know for certain that Chris would not have wanted his name or memory used in that connection," Commanday wrote to the newspaper. "I hope that there will be an immediate and permanent stop to this opportunistic and cynical use by the campaign."