A group of U.S. senators this week asked the Federal Communications Commission to step in and examine whether exclusive relationships between wireless carriers and handset makers are in the best interest of customers.

Four members of the Commerce Subcommittee on Communications, Technology and the Internet fired off a letter to FCC chairman Michael Copps on Monday, expressing their growing concern over the deals, like the one in place between Apple and AT&T regarding the iPhone.

Their request actually stems from a petition filed last month by the Rural Cellular Association, a group of smaller tier II and tier III wireless carriers that provide service to parts of the U.S. where tier I brands like AT&T, Verizon, Sprint and T-Mobile do not.

They argue that their inability to provide their customers with some of the most popular mobile handsets and smartphones makes it difficult for them to compete, especially in markets where their coverage does overlap with some of the big tier I operators.

In their letter to the FCC, the senators asked the commission to examine five specific issues carefully and act expeditiously should they find that exclusivity agreements unfairly restrict consumer choice or adversely impact competition in the commercial wireless marketplace.

Specifically, they request a determination on whether exclusivity agreements are becoming increasingly prevalent between dominant wireless carriers and handset manufacturers, and whether these agreements are restricting consumer choice, particularly for those living in rural America.