The UN's Committee of Decolonization disagrees: <https://en.wikipedia.org/wiki/United_Nations_list_of_Non-Sel....

Of course, that's only the most egregious controversy on that list, as you'd see if you scroll up a bit on that page to read the Criticism section.

I don't see where that conflicts with the previous claim. In particular, it's telling that the Manhasset negotiations didn't involve a Spanish delegation.

https://en.wikipedia.org/wiki/Manhasset_negotiations