By Malathi Nayak

NEW YORK (Reuters) - Wireless providers T-Mobile US Inc and Sprint Corp on Thursday introduced revamped plans that offer unlimited data, as wireless carriers step up efforts to woo customers.

T-Mobile said it will offer customers unlimited high-speed data starting at $70 per month for one phone that comes with DVD-quality video streaming. Those who want high-definition video have to pay $25 extra.

The new T-Mobile One plan will be available starting Sept 6.

Following T-Mobile's announcement, Sprint slashed prices on its unlimited data plans. Sprint said customers now have access to unlimited data for $60 per month for one phone, also with DVD-quality video, compared to a previous rate of $75 per month.

Sprint said its new plans would roll out on Aug. 19.

The moves come as wireless players are locked in an aggressive battle for subscribers in the saturated U.S. wireless market. Smaller rival Sprint has been offering half-off discounts and T-Mobile has launched free music and video streaming to lure customers away from competitors.

"We have one single offer that banishes data buckets forever," T-Mobile chief executive John Legere said in a video blog.

T-Mobile already offers users unlimited data for music and video streaming from services such as Netflix and Hulu.

On Wednesday, AT&T announced a revised data plan and eliminated overage fees for customers who surpass their data allowance.

AT&T currently offers unlimited data to its wireless customers who sign up for its DIRECTV television service.

In July, Verizon, which does not offer unlimited data, said that it would increase plan rates but expand data buckets by 30 percent for its customers.

Before announcing the new plan, T-Mobile had plans with data limits and also had cheaper unlimited data offerings such as a 6 gigabyte data plan with unlimited data for $65 per month.

T-Mobile would continue to sell its Simple Choice plans with data limits "for a while as we unwind them" and the older unlimited plans would not be available from Sept. 6, chief marketing officer Andrew Sherrard said in an interview.

With unlimited data, T-Mobile and Sprint provide video streaming of a quality lower than standard definition video.

Sprint conducted tests with customers who found the video experience "practically indistinguishable," chief executive Marcelo Claure said in a statement.

(Reporting by Malathi Nayak; Editing by Bill Trott)