Using SSH key with Sublime Text SFTP Plugin for Amazon EC2

Using SSH key with Sublime Text SFTP Plugin for Amazon EC2

Under Windows, how can you configure Sublime Text's FTP plugin to use an
SSH key (a .pem key for EC2) to upload files to the EC2 server via SFTP?
I am getting Connection Timeout error using the following config in
sftp-config.json:
"type": "sftp",
"host": "ec2-xx-xxx-xxx-xxx.compute-1.amazonaws.com",
"user": "ubuntu",
"ssh_key_file": "F:\\SSH Keys\\aws\\xxx.pem",