Police in South Korea have arrested a man accused of making an online threat to kill the US ambassador to Seoul, the Yonhap news agency reports.
The man, identified only by his surname Lee, allegedly posted the threat on the White House website earlier this month.
Yonhap said Lee, who denies guilt, was arrested on 14 July at the request of US authorities and found to have draft copies of the letter on his laptop.
Mr Lippert was injured in an knife attack in Seoul last year.
He suffered deep gashes to his face and hand when Korean nationalist Kim Ki-jong lunged at him with a knife at a breakfast meeting in a hotel.
Mr Kim is on trial for a string of charges linked to the attack.
‘US appreciative of Korean action’
Yonhap said that as well as the draft letter – the details of which have not been made public – Mr Lee’s confiscated laptop showed he had visited the White House homepage and was storing a screen grab of when he posted the letter.
Police told Yonhap they believed he was acting alone.
A spokeswoman at the US embassy told the BBC the threat had not affected Mr Lippert’s activities as ambassador.
She said the US appreciated the “quick action of the Korean authorities of looking into this and identifying a suspect,” and that US law enforcement agencies were co-operating with South Korea on the investigation.