WASHINGTON - Federal regulators have given Verizon Communications Inc. the green light to sell nearly 5 million phone lines in 14 states outside of its core service areas to Frontier Communications Corp.

Friday's approval by the Federal Communications Commission marks the final step for the $8.6 billion cash-and-stock deal, which was announced more than a year ago and is expected to close on July 1. The transaction has been cleared by antitrust regulators at the Justice Department and Federal Trade Commission, as well by as state regulators and local officials.

Verizon is selling 4.8 million residential and small-business phone lines and 1 million broadband connections in rural and small-town markets to Frontier. The deal will nearly triple the customer base for Frontier, which is based in Stamford, Conn.

In return for FCC approval, Frontier has pledged to make significant investments in high-speed Internet networks. Expanding broadband availability, particularly in rural America, is a top priority for FCC Chairman Julius Genachowski.

The companies have also pledged to honor all of Verizon's existing contracts to provide wholesale telecommunications services.

The sale includes all of Verizon's phone lines in Arizona, Idaho, Illinois, Indiana, Michigan, Nevada, North Carolina, Ohio, Oregon, South Carolina, Washington, West Virginia and Wisconsin as well as some assets in border areas of California.

Verizon has been selling off assets outside of its primary footprint in the Northeast and California, even as it has been installing fiber-optic lines that deliver high-speed Internet connections and subscription video services in its core markets.