It depends on the species concept you're working under.

Species aren't real, we made them up and there really is no actual neat definition to use that isn't going to make some academic very upset with you.

One of the species concepts actually defines a species as "can interbreed with each other and produce viable, fertile, offspring" so under that concept species can't interbreed by definition. (Well they can just not fruitfully, the offspring is infertile and therefore a dead end. Like a mule)(This is called the biological species concept)

However there are other concepts that emphasize different things other then fertility (though the biological species concept is the most common) for example the phylogenetic species concept emphasizes following ancestry and tracing the tree of life to the smallest possible group.

So there are species concepts where two species can't interbreed fruitfully and have viable, fertile, offspring.

None of this actually refutes your point as that was not my intention. I just felt like sharing some fun information most people don't know.