The invention relates to a burner having an annular premixing channel in which fuel can be discharged in a radially distributed manner. The radial distribution of the fuel can be regulated during operation of the burner in that fuel can be supplied, independently of one another, into a first and a second part of admission devices having admission holes varying radially in opposite direction by means of fuel supply lines. The invention also relates to a method for operating a gas turbine in which radial distribution of the fuel is regulated in a premixing channel of a burner.