# LetterSpace without \usepackage{fontspec}

I need to increase the LetterSpace of a piece of my text.

I know that it is possible with this code:

\usepackage{fontspec}
\NewDocumentCommand{\allcaps}{m}{%
}


But this code has to be run with LuaLaTeX (or maybe also XeLaTeX or others) but not with LaTeX.

Because I would like to keep running with LaTeX (otherwise the result will be different), in which other way I can modify the LetterSpace of a text?

\documentclass[10pt]{article}