Adele is sitting on ''massive'' hits, according to singer songwriter Ryan Tedder.

The 'Counting Stars' musician - who has worked with the British powerhouse on her latest LP '25' - has revealed the 'Hello' hitmaker has recorded a number of tracks, which she hasn't included on the album yet.

Speaking to The Times newspaper about the songstress, the 37 year old said: ''She [Adele] passed on a lot of hits for this album [25].

''Max Martin and I are both sitting on songs that could be massive. This the power of Adele and Beyonce: When you can cast aside hit after hit in exchange for pure honesty.''

However, Tedder has revealed he struggled to produce Adele's music because all of her records sound like a ''hit''.

He said: ''It's difficult to produce Adele because everything she sings sounds like a hit, so it's a lot harder on the songwriting process. She could sing 'Feliz Cumpleaños' in Spanish and somehow you go: 'That is probably a top 10'.

And the OneRepublic frontman - who has worked with Beyoncé, Whitney Houston and Jennifer Hudson on songs - has revealed he is very selective about who he partners with and will ''only'' work with an artist whose music he ''genuinely'' likes to listen to.

He explained: ''I only work with people I genuinely listen to or like.''