RUS administrator Jonathan Adelstein said his agency was working to find the right definition for geographic areas eligible for the new funding, approved in the American Recovery and Reinvestment Act, a huge economic stimulus package. But before McCaskill spoke, three other senators complained that the RUS, in defining "remote" areas eligible for a targeted grant program as those that are 50 miles outside cities, was leaving out large areas now unserved by broadband.

There are large sections of Arkansas that aren't covered by broadband, but only a couple of areas that would be eligible for the remote grants, said Senator Mark Pryor, an Arkansas Democrat.

Adelstein said the RUS is trying to rework the definition of remote areas, for which $400 million is set aside for last-mile projects.

"It turns out maybe we went too far, and a lot of West Virginia wasn't counted and a lot of Arkansas wasn't counted," Adelstein said. "Our goal is, I think, shared, which is that those funds reach the hardest-to-reach areas."

In addition to concerns from senators, the U.S. Government Accountability Office (GAO) Tuesday saying the two agencies face several challenges in meeting congressional deadlines for distributing the $7.2 billion.