Sprint and T-Mobile shares sank on Monday after Nikkei reported that SoftBank Group planned to end negotiations for a merger between the two wireless carriers.
Trading of Sprint, a subsidiary of the Japanese telecom firm SoftBank, was halted for volatility before the shares fell by as much as 13%. T-Mobile fell by as much as 4%.
SoftBank could approach Deutsche Telekom, T-Mobile's owner, as early as Tuesday to propose ending the negotiations, Nikkei reported. Deutsche Telekom wanted a controlling stake in the combined company, but SoftBank's board agreed Friday that it preferred to retain control, the report said.
SoftBank looked into buying T-Mobile as far back as 2014, but backed down after telecom regulators made it clear they would block any acquisition of the fourth-largest US carrier.