New Zealand's teenage running star says he wants to go even faster .. after another Worlds' best

Sam Ruthe, who's just 16, ran 3 minutes 48 point 88 at an indoor meet at Boston University.

Domestically, he beats Sir John Walker's record from 1982 by two tenths of a second, it's also the fastest-ever indoor mile by a high school student ...and an under 18 World Record for the Mile.

Ruthe says the race was meant to be a rust-buster.