ibtool to update .strings from .strings?

Question

Is it possible to use ibtool to update a localized .strings file with an updated .strings file from the original language?

Concrete use case:

1. We have one base .xib, and multiple .strings files for each language
2. All strings files are translated for app version A
3. For app version B new strings are now added to the base .xib
4. We create a new (base) .strings file via ibtool

Now we'd like to

• update the already translated .strings files with just the new entries from the base strings file that have not yet been translated,
• but keep the translated text.

All examples I could find support incremental localization only if there are multiple .xib files for base and localizations.

Is it possible to use ibtool to basically just add the new strings to the already localized .strings files?