WASHINGTON (Reuters) - The head of the U.S. Federal Communications Commission has put on hold a plan to revise the rules governing the right of small wireless phone carriers to "roam" on the networks of larger rivals.

At issue is whether carriers should be allowed to roam in areas where they own airwaves, but have not built networks.

FCC Chairman Kevin Martin had proposed guaranteeing that carriers who owned unused spectrum could continue roaming for four years before they lost roaming rights.

But he withdrew the proposal before a meeting of the FCC's five commissioners on Friday because they had not reached an agreement on the issue.

"At this point, I'm not sure I see a consensus for how the commission ends up addressing it," Martin said in a telephone interview with Reuters.

The move also comes after small carriers such as Leap Wireless International Inc asked the FCC to ban Verizon Wireless' plan to buy Alltel unless rules are put in place to make sure consumers are not left without roaming in some areas.

Verizon, which hopes to close the Alltel deal by year-end, declined comment beyond documents it filed recently with the FCC promising to maintain Alltel's roaming agreements.

The FCC review of the rules stems from an order it adopted last year that reaffirmed the rights of smaller carriers to roam on the networks of bigger wireless companies such as AT&T Inc and Verizon Wireless, a venture of Verizon Communications Inc Vodafone Group Plc.

Martin said the rules were designed to encourage companies to make use of the airwaves they own, rather than just sitting on them and roaming on the networks of other companies.

He said he proposed the revisions in response to concerns by some smaller wireless carriers that there were areas where they had acquired spectrum, but did not have access to it. These carriers argued they should be able to maintain their right to roam in those areas.

Martin said carriers could use the four-year grace period before their roaming rights expired to build out their own networks or to give the spectrum back to the government and continue roaming.

But other commissioners had reservations about some of the provisions. Some have proposed giving roaming carriers a longer phase-in period and others said they needed more time to study the issue.

Leap's Director of Government Affairs, Laurie Itkin, said in an e-mailed statement she expected the commissioners to reach a consensus on roaming rules before deciding on the Verizon/Alltel deal.

AT&T was not immediately available for comment.

(Additional reporting by Sinead Carew in New York)

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