The Bourne Ultimatum actor explained that he struck up a close friendship with Blunt while shooting the action-packed romance, which only resulted in complications when the time came for them to finally lock lips.
He told Today Show host Meredith Vieira: "By the time we shot that scene, it was really one of the last things we shot and we were really great friends and our spouses were really great friends and it was very, very, very, awkward.
"John Toll, the great cinematographer and also a friend of ours, he was shooting the film and he was equally uncomfortable. He was saying 'Guys it's only seven seconds, can you just give me seven seconds?'"
The Adjustment Bureau opens in the UK and US on March 4.
> Blunt happy to finish 'Bureau' shoot