Embed XML from file into RMD - r-markdown

Question

I have an XML file (SOME.XML), the contents of which I would like to embed in an .RMD document.
If I was content with having the XML reside directly within the .RMD, I'm aware that I could simply do:
```xml
---some xml here---
```
My embarassing attempts so far are:
```{xml code=readr::read_file('SOME.XML')}
```
...which failed as there is no XML engine.
I have also tried:
````{r results='asis'}
cat('```xml')
cat(readr::read_file('SOME.XML'))
cat('```')
````
...for which, although the knitting completes, the output is not at all correct.
Is this possible? (No doubt there is some trick here that I am missing!)
If needed, I could have a pre-knit stage where the content of the XML file is substituted in before subsequently passing a modified version of the .RMD to rmarkdown::render. However, I'd like to avoid this if possible.
Update:
Using readLines as proposed by the answer is complaining about ...incomplete final line found on 'SOME.XML'. Using readr::read_file() avoids this for me. For my particular project, I am now using:
```xml
`r readr::read_file("SOME.XML")`
```
Thank you to #user2554330 for the elegant solution!

Answer 1

Here's one way to do it:
```xml
`r paste(readLines("SOME.XML"), collapse = "\n")`
```
The idea is to put the XML into inline R code. I think knitr ignores the chunk wrappers because they aren't in the {xml ... format it looks for, but it will see the inline code and expand it. Then Pandoc will handle the formatting.
Here's how to modify your approach to get it to work:
````{r results='asis', echo = FALSE}
cat('```xml\n')
cat(readr::read_file('SOME.XML'), sep = "\n")
cat('\n```\n')
````