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July 10 (Reuters) - EasyJet EZJ.L has agreed in principle to a £5.7 billion ($7.65 billion) takeover approach from Apollo Global APO.N, the British budget airline said on Friday, ditching a lower bid from rival suitor Castlelake.

Apollo's proposal of about £7.15 per easyJet share is about 3.6% higher than Castlelake's latest bid and could mark the start of a takeover battle for the London-listed carrier.

The easyJet board said it was no longer minded to recommend Castlelake's proposal of £6.90 per share, which the two sides had agreed in principle only days earlier.

"The proposed cash offer delivers a superior outcome for easyJet shareholders by providing a higher cash value than Castlelake's latest proposal," easyJet and Apollo said in a joint statement.

Apollo must announce a firm offer for easyJet by August 7 or walk away. Castlelake has until August 3.

"Apollo believes in easyJet’s existing strategy of evolving and strengthening the low-cost carrier model," Apollo said.

($1 = £0.7447)