Phelps may have already claimed 14 Olympic titles, but Florida-based Lochte won five gold medals at last year's World Championships in Shanghai.
Two of those victories saw him edge out his fellow USA athlete. In the 200m Individual Medley, he became the first swimmer to break a long-course world record since turbo suits were banned. He also triumphed in the 200m Freestyle.
While Phelps has dropped the latter event in London, the duo are scheduled to meet on Saturday in the 400m Individual Medley before the shorter 200m Individual Medley on 2 August, the day before Lochte's 28th birthday.
At a USA press conference, Lochte said: 'I'm not really going just to swim to beat Michael.
'Michael is just one person and there are a bunch of other swimmers across the world I have to worry about.
'I am just doing what I normally do and I am just going to go up on the blocks and race and have fun.
'If Michael's right there with me then he is right there with me but I can't just rely on one person.
'Back home people are talking about me and Michael - I guess that is just talk and I guess I shall just see what happens in a couple of days.'