Verizon Wireless will introduce a new unlimited prepaid plan nationally this week, taking on rivals Sprint Nextel Corp. and MetroPCS Communications Inc. as they continue to add customers seeking contract-free service.

Verizon Wireless will begin offering the plan—which includes unlimited talk, text and Web use for $50 a month—on Thursday, said spokeswoman Brenda Raney. In addition to Verizon stores, it will be sold at Best Buy Co., Wal-Mart Stores Inc. and Target Corp. locations.

Verizon is making the push into unlimited prepaid plans as the category drives customer growth on Sprint's Virgin Mobile and Boost brands, as well as MetroPCS. Prepaid plans, which have historically been marketed to lower-income customers, are becoming more attractive as the cost declines and phone choices improve.

Such plans still make up a small percentage of Verizon's business. As of the end of June, Verizon had 4.4 million prepaid customers, 3.4% fewer than a year earlier, while it boosted its more lucrative contract users by 4.6% to 85.3 million. By contrast, Sprint lifted its prepaid subscriber rolls in the period by 23% to 13.8 million, about a quarter of its total customers, while MetroPCS added 19% to 9.1 million.

"This is a very competitive market, and we want to make sure we have a price portfolio to fit a greater number of customers," Ms. Raney said. "In these times, there are some people who would prefer living on a prepaid plan."