Hor Namhong summoned the US Charge d?Affaires in Phnom Penh, Jeff Daigle, on Thursday to complain about the "highly defamatory" 2002 cable, which was released via WikiLeaks this week, the foreign ministry statement said.
In the meeting, the Cambodian asked Daigle "to convey to the US State Department his strong protest" over the cable, "which is full of unacceptable maligned indictment", the ministry said.
The cable cites an "undated, unattributed report" on file at the US embassy, which said Hor Namhong took charge of Boeung Trabek camp in the capital after the brutal communist movement took power in 1975.
"Hor Namhong came back to Cambodia after the Khmer Rouge took over, but was not killed because he was a schoolmate of Ieng Sary," the report said, referring to the regime's ex-foreign minister now on trial for genocide.
Hor Namhong "became head of the Beng Trabek (sic) camp and he and his wife collaborated in the killing of many prisoners," it added.
The minister himself has long said that he and his family were prisoners at a Khmer Rouge camp, and he has successfully sued people in the past for claiming that he had links to the blood-soaked communist movement.
The US embassy in Cambodia confirmed that Daigle met Hor Namhong on Thursday but said it was unable to comment on the content of any allegedly leaked US government documents.
Up to two million people died of overwork and starvation or were executed under the Khmer Rouge, which outlawed religion, property rights, currency and schools during its four-year rule.
A number of the current administration in Cambodia had links to the regime, and Prime Minister Hun Sen himself was mid-level Khmer Rouge cadre.
In April, a Cambodian court slapped opposition leader Sam Rainsy -- who lives in exile in France -- with a jail term and a fine for accusing Hor Namhong of being a former regime member.
He was found guilty in absentia of defamation and inciting discrimination for claiming in a 2008 speech that Hor Namhong once belonged to the movement.
Sam Rainsy, seen as the main rival to Hun Sen, has been convicted by Cambodian courts on various other counts, which his party and rights groups say are an attempt to sideline him ahead of elections in 2013.
In May 2010, a French appeals court upheld a guilty verdict against Rainsy for remarks in his autobiography about the foreign minister's alleged role in the movement, but the French Supreme Court overturned the decision last April.