Error accessing GCP Cloud Storage public object

Question

I'm getting following error while reading SSL cert file from GCP Cloud Storage.

* Connected to [my.website.com] (A.b.C.D) port 443 (#0)
* found 6 certificates in /home/<username>/[CAINFO].crt
* found 597 certificates in /etc/ssl/certs
* ALPN, offering http/1.1
* error reading X.509 key or certificate file: Error while reading file.
* Closing connection 0
Error: SSL connect error
    at Error (native)
file." 

Here's what I'm doing.

1. In NodeJS code, I'm pinging an API end point while authenticating with SSL certs
2. I have an SSL cert stored in GCP Cloud Storage and made it Public (just for testing) following instructions given here.
3. Instructions to access this object is given here.

4. Using gsutil, I am able to access the cert.

   $ gsutil ls -r gs://[BUCKET_NAME]/[SSLCERT].pem gs://[BUCKET_NAME]/[SSLCERT].pem

5. When I access the SSL cert from NodeJS code, I get above error. The URL to access the file is: http://storage.googleapis.com/[BUCKET_NAME]/[SSLCERT].pem

6. Instead of Cloud Storage, if I access the cert from local disk and run NodeJS code, it works fine. So, the cert is valid.

Outline of my code:

const Curl = require('node-libcurl').Curl;
const curl = new Curl();

const URL = 'https://api-end-point.com';

// let sslcert = '/home/path/to/[SSLCERT].pem';  << this works
let sslcert = 'http://storage.googleapis.com/[BUCKET_NAME]/[SSLCERT].pem';  << NOT working

curl.setOpt('URL', URL);
... 
curl.setOpt('SSLCERT', sslcert);
... 

curl.on('end', function(statusCode, body, headers) {

    console.info("Status Code: " + statusCode);
    console.info(body.length);
    this.close();
}); 

curl.on('error', (err) => {
    console.log(err);
}); 

curl.perform();