Verizon Wireless would be willing to make a compromise on roaming service agreements with smaller mobile operators, according to a letter it sent on Wednesday after pressure from U.S. lawmakers.

The venture of Verizon Communications and Vodafone Group said it was proposing a new rule in response to lawmakers' concerns that current roaming regulations put small service providers at a disadvantage.

When phone users travel outside the coverage area of their own service provider's network, roaming agreements allow them to use another carrier's network.

Currently, wireless providers are not required to offer roaming services to rivals in areas where those rivals own wireless airwaves but have yet to build network coverage, according to Verizon Wireless, the No. 1 U.S. mobile service.

But the company said in the letter, obtained by Reuters, that it would support a new law requiring it to provide rivals with roaming services in places it is not currently obliged to offer such services.

It suggested a time limit of two years for the requirement, except when special conditions applied that could make some operators eligible for a third year of roaming services.

Smaller rivals such as Leap Wireless have complained about rules governing roaming.

However, Leap's director of government affairs, Laurie Itkin, said roaming agreements with time limits would not be enough.

Verizon itself has relied on roaming agreements for over two decades as it built out its network and acquired competitors, but now has unilaterally decided that its remaining competitors are only entitled to roaming for two or three years, Itkin said in an emailed statement.

Verizon's letter which was sent to representatives Rick Boucher, Henry Waxman, Joe Barton and Cliff Stearns, appeared to be the company's second effort in a week to preempt regulatory changes by making its own proposals.

Last week, Verizon offered to limit its exclusive handset deals to help smaller companies.

This came after pressure from U.S. lawmakers and small carriers and reports that the Department of Justice was taking a preliminary look at whether agreements between operators and phone makers were anti-competitive.

(Reporting by Sinead Carew; Editing by Gary Hill and Muralikumar Anantharaman)