Beyonce is putting pressure on herself to make her next single ''a classic''.

The 31-year-old singer has delayed the follow-up to 2011 album '4' several times because she is a ''perfectionist'' and determined the lead track from the record be as good as 'Single Ladies (Put A Ring On It)', which went four-times platinum in 2008.

A source told The Sun newspaper: ''Beyonce is a perfectionist - and her biggest competition is herself.

''She won't put anything out as her first single until she's 100 per cent sure it will be a classic. She's putting pressure on herself for it to be a hit of 'Single Ladies' calibre, and to make sure she's on top of the game.''

The original proposed first single, 'Grown Woman' is now being used as a teaser for a Pepsi commercial, while 'Bow Down' was also dropped after controversy over its lyrics.

The track was previewed on Beyonce's website last month and included lines such as: ''I know when you were little girls you dreamt of being in my world / Don't forget it / Respect that / Bow Down b****es.''

Elsewhere she sings: ''I took my time to live my life but don't think I'm just his little wife / Don't get it twisted this is my s**t.''

One outraged Twitter user slammed: ''how can u sing at the presidents inauguration then release this disgusting, offensive song @beyonce? I'm genuinely shocked (sic)''