US FCC to carriers: Change numbers in 1 day, not 4

* FCC rule changes requires one-day transfer for numbers

* Verizon, T-Mobile say rule easy to comply with

WASHINGTON, May 13 (Reuters) - Landline, wireless and most voice over Internet (VoIP) providers will soon be required to transfer customers' telephone numbers to new carriers within one day, if requested, the U.S. Federal Communications Commission said on Wednesday.

Currently, carriers have four days to transfer telephone numbers. The changed rule requires most carriers to begin one- day transfers within nine months. Some smaller carriers will have 15 months.

A growing number of people in the United States are forgoing landlines and switching their numbers to wireless and Internet providers.

Mid-sized carriers such as Deutsche Telekom AG's (DTEGn.DE: Quote, Profile, Research) T-Mobile [TMOG.UL], and Sprint Nextel Corp (S.N: Quote, Profile, Research), had accused landline companies of sometimes delaying "porting," or providing the number to the new carrier, in an attempt to woo the customer back.

"For a number of years now, wireless carriers have been porting numbers between themselves in a matter of hours," said Commissioner Jonathan Adelstein in a statement. "Simply put, consumers should be able to port a number quickly no matter who their carrier is.

Both T-Mobile and Verizon Communications Inc (VZ.N: Quote, Profile, Research) quickly issued statements supporting the quicker shift.

"Verizon will work with the FCC and the industry to help make this new system work well for consumers. Verizon meets current requests over 99 percent of the time and we will aim to continue this record," spokesman David Fish said in a statement.

T-Mobile USA vice president for government affairs Tom Sugrue said: "T-Mobile applauds the leadership of the FCC today for reducing the wireline to wireless porting interval to one day. We look forward to working with the commission and the NANC (North American Number Council) to facilitate a rapid and smooth transition." (Reporting by Diane Bartz; Editing by Andre Grenon)