State antitrust officials also have qualms with the merger, according to one of the WSJ's tipsters. The FCC is on record as having questions about both the claimed cost savings and their plans for wireless home broadband.

T-Mobile and Sprint didn't have an immediate comment on the apparent leaks.

If the report proves true, it could signal major trouble for the merger. The networks had hoped to complete their corporate matrimony before July (after previously aiming for April). If they have to make substantial changes like selling business assets, they might have to wait considerably longer. And that's assuming they're willing to change the agreement in the first place. Should they feel the requests go a step too far, they might repeat history and scrap the merger effort altogether.