The two singer-songwriters became friends last year, during Sheeran's year off and Blunt was at a party with the "Lego House" star when he was nicked on the face by a sword, reported NME magazine.
"Ed and James have a real laugh together, it'll be proper madness on tour. James has a good following in the US so he'll also play some gigs too, acting as a support for his mate," a source said.
The duo are also working on new material for Blunt's new album.
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