How To provide Cancel upload option with html5 file api

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C#

HTML5

MVC3

I am uploading file with html 5 file api..but in progress event i want to cancel the upload then how it can be done...my code is..

// Update progress bar
xhr.upload.addEventListener("progress", uploadProgress, false);

function uploadProgress(evt) {

    if (evt.lengthComputable) {

        var percentComplete = Math.round(evt.loaded * 100 / evt.total);
        prognumber.innerHTML = percentComplete + '%';


        //assign value to prgress bar Div
        var progressBar = document.getElementById("progressBar");

        progressBar.max = evt.total;
        progressBar.value = evt.loaded;
    }
}

// File load event
xhr.upload.addEventListener("load", loadSuccess, false);

function loadSuccess(evt) {
    prognumber.innerHTML += "Upload";

}

I want to provide cancel upload option...