Groupon announced on Tuesday that it is expanding its Groupon Reserve channel to the Groupon mobile app. For now, it’s only available on the iPhone app, but the company says it plans to add the feature to Android and iPad soon.

According to a Groupon spokesperson, 45% of North American transactions were completed on mobile devices, compared to 30% in March 2012. In Q1, less than 45% of Groupon’s North American transactions came from email, with mobile and search accounting for a greater percentage. North American mobile customers spend on average well over 50% more than web-only customers, he says, adding that over 40 million people have downloaded the Groupon mobile app, including 7 million in Q1 alone.

“We’ve also seen increased interest from merchants since the Web launch of Groupon Reserve,” the spokesperson says. “In fact, July 1 (date of the Web announcement) was one of the highest trafficked days in the history of our B2B website www.grouponworks.com.”

Groupon Reserve is based on Savored.com’s reservations engine, which lets customers book tables at restaurants and get big discounts. Groupon acquired Savored last year. More on the Groupon Reserve launch here.

With the new iPhone experience, users can make, view, share and modify restaurant reservations in the currently available markets, which include: Atlanta, Boston, Chicago, Denver, Los Angeles, Miami, New York City, Philadelphia, San Francisco and Washington D.C.

“Since the launch of Reserve, we have seen a significant increase in bookings, and adding the capability to the Groupon mobile app will make it even easier for more customers to reserve a great dining experience at some of the best restaurants in their city,” said Ben McKean, GM of Groupon Reserve reservations. “Reserve on mobile gives our customers even more options for great things to do wherever they are.”

Groupon says it intends to launch Reserve in more cities in the U.S. and other key international markets. In the future it will also be expanded to include offerings from beauty, product, travel and entertainment brands, as well as spas, salons and hotels.