What Does It Mean To Sign A Letter Of Intent?

I am in the middle of negotiations between two academic institutions in Mexico to collaborate. On the one hand I should go directly to sources of support to get the money and make an offer that my counterparts cannot refuse, on the other hand, why should I start a long process and maybe drain my resources, for a partnership the counterpart does not feel eager to see completed.

I am still waiting for some kind of signed go ahead from my friends on the other side.

That I want to call a Letter of Intent. In Mexico we call it Convenio, from the same Latin word in convenience.