The charitable foundation of late US president Ronald Reagan has condemned a British auction house for selling a vial that purportedly contains his blood.
Bids above £6,000 have been made for the specimen vial and supporting documentation, apparently from the hospital where the then president was treated after a 1981 assassination attempt.
"If indeed this story is true, it's a craven act and we will use every legal means to stop its sale or purchase," Ronald Reagan Presidential Foundation executive director John Heubusch said in a statement.
The macabre memorabilia has been promoted on the Bristol-based website of Paul Fraser Collectibles and conducted by its Guernsey associate, PFC Auctions .
Both websites are registered to Paul Fraser in the Channel Isles.
The auction for the green-capped vial and letter from Bio-Science Laboratories is due to run until May 24.
PFC Auctions said the vial of dried residue was taken at George Washington University Hospital on March 30, 1981, after Mr Reagan was shot by John Hinckley Jr.
The provenance letter explained that the seller's late mother had worked at the medical lab where the presidential blood was examined.
The auction website showed a picture of the blood-filled vial with a typed label stuck to it showing the president's name.
Mr Reagan suffered a punctured lung and internal bleeding when he was shot by Hinckley outside the Washington Hilton Hotel.
Three other officials were shot but Hinckley was later found not guilty of 13 charges by reason of insanity.
Mr Heubusch said the presidential foundation had spoken to the hospital where Mr Reagan was treated and assured an investigation was under way into "how something like this could possibly happen".
But according to the seller's provenance letter, attempts were made to discuss the item with the Reagan representatives.
The seller said in the letter: "I said am I in any kind of trouble or will there be some black cars/SUVs or helicopters hovering above my home?"
"He called back in 25 minutes and said that everything was ok, National Archives was not interested in what I had, nor was the Secret Service , the FBI and other agencies."
PFC Auctions told Sky News Online: "We have not had any contact from The Reagan Foundation.
"The letter of provenance states that the original owner of the vial contacted the Reagan National Library - run by the foundation - and was told that they would accept the item as a donation, but that they would not pay for it."
The seller explained in the letter: "I told him that I didn't think that was something that I was going to consider, since I had served under President Reagan when he was my Commander in Chief when I was in the army from '87-'91.
"And that I was a real fan of Reaganomics and felt that Pres Reagan himself would rather see me sell it rather than donating it."