http://www.americanexpress.com/us/co...pass/faqs.html

In addition to the MoneyPak/VR, the FAQ also states this:

How do you reload with American Express® Card?

You can reload the PASS Card using an American Express® Card that is issued in the United States and is associated with a U.S. billing address. Please note that the type of funding source that American Express accepts may change from time to time. For more information, see the Cardmember Agreement.