The 40-year-old has the boys in the competition while Rowland, 30, has the girls.
He said to UK newspaper Daily Star: 'I get on with Kelly, well, I did until this point. When she got given her girls category at boot camp, I've noticed the texts have stopped.
'It's all gone into a new gear. It's war now. But that's fair enough.'
He added: 'The great thing is when I get home I've got nothing in my diary other than this show. I think I'm lucky. I already know Kelly's on tour with Chris Brown. That's good for me.
'I'm thinking: 'You go on tour while I work here.' I know the girls are a brilliant category so we've got to work on our plan of eliminating someone. But I'm confident we've got the winner in this category.'