WASHINGTON (Reuters) - The U.S. Federal Communications Commission said on Thursday it will approve the T-Mobile US Inc ( TMUS ) deal to buy Ka'ena Corp, the owner of budget service provider Mint Mobile, for up to $1.35 billion.

The FCC cited T-Mobile's voluntary agreement to implement a 60-day unlocking period for all Mint Mobile and Ultra Mobile devices activated on the T-Mobile network before and after the closing.

The FCC said the agreement will make it easier for Mint Mobile and Ultra Mobile customers to switch service providers.