U2 have been working on a new album for months.
The 'Elevation' rockers are writing tracks for their 13th studio album - with the working title '10 Reasons To Exist' - which will be their first release since 2009's 'No Line on the Horizon'.
Singer Bono told The Sun newspaper: "U2 have been back and they're really in fine fettle.
"They're mad for it at the moment and they really want to make a new record. And they don't care if it takes ten years - they don't care if it never happens again, they just want to get it right.
"Within the band we've been calling it '10 Reasons To Exist' - but I will tell you we might have at least six of them."
Bono added the band had halted recording in December as he got flu.
U2 - which also includes The Edge, Adam Clayton and Larry Mullen - completed their 360 Degree tour, the highest grossing of all time, in 2011, and then took time off to rest and recuperate.
Bono took his family on a round the world trip of the world's most spiritual regions, which may have influenced him for the band's new album.
Speaking about the trip Bono said: "Because I wasn't busy with the band we kind of went wandering. Once in a lifetime sort of stuff, places like Africa and Central America.
"We also went to Jordan and Israel and Peru. It was really great to have time off."