DRAE , Dictionary of the Royal Spanish Academy, defines the former as "appoint someone to an obligation, be responsible for something" or "make a commitment"; whereas the latter is conceived as "force oneself to do, say, or give something".
El DRAE define el primero como "constituir a alguien en una obligación, hacerse responsable de algo" o "contraer un compromiso". El segundo se concibe como "obligarse a hacer, decir o dar algo".