A spokesman for the company said: "Kelley can sell the photographs of Marilyn Monroe if he wants, but that is all he is selling."
The pictures are expected to cause a stir in their own right, but it is Monroe's signature on a standard model release form that is causing the row.
Monroe's estate disputes that this signature still gives over the right to manipulate and use the images for commercial use.
But Tom Kelley Jr, whose father took the photographs, insists that by signing the form she gave over all commercial rights, which could prove very lucrative.
"There's still a very strong interest in Marilyn Monroe, for fan clubs, celebrity endorsements, and it is not going to get any smaller," said Kelley Jr.
'Minimal value'
CMG Worldwide Inc, which represents the Monroe estate, is planning legal action to prevent commercial use of the pictures.
A spokesman for the company said: "Kelley can sell the photographs of Marilyn Monroe if he wants, but that is all he is selling."
"There are tens of thousands of original photographs of Marilyn Monroe out there and we just think an eight by 10 inch transparency has minimal value."
Monroe left her name and image to her acting coach Lee Strasberg and a psychiatric institute in London.
Strasberg's widow and the Anna Freud centre continue to hold these rights and are represented by CMG, which also acts as the business agent for Italian screen legend Sophia Loren.
Kelley's own agent, Gary Saal, still maintains that any prospective buyer of the photos, will get to use them as they want.
"Say for the sake of discussion, someone wanted to take the image of Marilyn Monroe and dress her up, turn her into a moving image and have her purchase an airline ticket," he said.
"With the model release form, you are allowed to create derivative images. Moving figures? Absolutely."
Online site eBay is to hold an internet auction alongside a traditional sale at the Butterfields auction house in Los Angeles on 22 March.
They are not speculating as to the value of the so-called Red Velvet photo series, and the accompanying model release form bearing Monroe's loopy signature.