Based on the stringi::stri_pad and tools::showNonASCII

str-pad.R

str_pad <- function(str, width = floor(0.9 * getOption("width")), side = c("left", "both", "right")) {
    side <- match.arg(side)
    asc <- iconv(str, "latin1", "ASCII")
    if (any(is.na(asc) | asc != str))
        width <- width + nchar(str, "bytes") - nchar(str, "width")
    switch(side,
           left = sprintf("%*s", width, str),
           right = sprintf("%-*s", width, str),
           both = sprintf("%-*s", width, sprintf("%*s", floor(width / 2), str)))
}

Example:

paste(str_pad("One", 20), 1)
#> [1] "One                  1"
paste(str_pad("Один", 20), 1)
#> [1] "Один                 1"