New York City: Roger Stone has taken aim at the US federal judge overseeing his criminal case, blasting her as a partisan Barack Obama appointee and posting a photo of her face featuring what appeared to be a cross-hairs symbol.

The embattled confidant to President Donald Trump posted the picture of Washington, DC, Judge Amy Berman Jackson on Instagram but quickly deleted it after the New York Daily News asked about the apparent rifle scope symbol in the left hand corner.

Stone, who was indicted in Special Counsel Robert Mueller's Russia investigation last month, claimed he "didn't notice the symbol in the corner".

"I saw no such thing," Stone told the Daily News. "It is simply a photo of the Judge off the Internet."

Minutes later, Stone deleted the photo and replaced it with one cropping out the cross-hairs.

"Special counsel Robert Mueller used legal trickery to ensure that my upcoming show trial is before Obama appointed judge Amy Berman Jackson," Stone captioned the new post.

DPA