Groupon Payments is aimed mainly at businesses that offer deals through the Groupon. 

A test program, however, allows other merchants to use the service at higher rates. With its launch of the service Wednesday, Groupon Inc. is going up against services like PayPal and Twitter co-founder Jack Dorsey's Square, which make it easier for merchants to accept credit cards with a simple phone attachment. 

The online deals company has seen a sharp decline in its stock price since going public late last year.

With Groupon Payments, the Chicago company is trying to broaden the array of services it offers to merchants.

(Copyright 2012 by The Associated Press. All Rights Reserved.)