American Express is giving cardholders who also use Twitter a good reason to sync the two services, with the ability to purchase gift cards and products using only a hashtag.

American Express announced Monday that eligible cardholders will now have yet another perk to add to their exclusive membership by enabling hashtag purchases via Sync with Twitter.

To encourage cardholders to sync their accounts with Twitter, American Express briefly offered a $25 gift card for only $15, but it was already sold out by the time we synced our own account and tweeted the hashtag #BuyAmexGiftCard25.

Starting at noon EST on Wednesday, Feb. 13, American Express will expand the promotion to include select products from Amazon, Sony, Urban Zen and Microsoft at discounted prices, including a $149.99 Kindle Fire HD (while supplies last, expires March 3, 2013).

How it works

To participate, cardholders first sync their account to Twitter, then tweet a special product hashtag from the product they wish to purchase with their Amex card.

American Express will then reply via the @AmexSync account with a confirmation hashtag, after which time users have 15 minutes to tweet their own response.

Once confirmed, the purchase will be charged to the synced card and sent to the billing address on file via free two-day shipping courtesy of American Express.

American Express Sync with Twitter was launched last year as a way for cardholders to earn discounts just for posting tweets with hashtags tied to select products.