Locutionary Force is the innate force or meaning of a message, as opposed to its effect on the listener and his status or function as an action.
John L. Austin distinguishes the Locutionary force of sentences from their illocutionary and perlocutionary force.
If I say, “You can trust me, I will be there,” the Locutionary Force of this message is nothing more than what those words mean.
In most contexts, such a sentence will form a promise: By saying the words, I am effectively doing something, namely producing a promise. This will be the illocutionary force of my sentence. Finally, the effect of this sentence on my listener, say, instilling confidence in me that I will come where you agree to meet, is the perlocutionary force of my words.