The US federal communications commission is due to start an auction for low-frequency airwaves at the end of this month, which industry observers expect could last for months.
“During that period, there will be no M&A activity in the US telecoms sector,” said one person familiar with the situation on Tuesday.
Auction participants are not allowed to engage in any partnership or merger talks during the weeks before and after the bidding process. T-Mobile US, which is 65.4% owned by Deutsche Telekom, has said it could spend up to $10 billion in the auction.
An auction of AWS-3 airwaves, which ended early last year, raised a record $44.9 billion.
Deutsche Telekom, which declined to comment, has been trying to sell the unit for years, hoping to cash in on a recovery in the business.
Last month T-Mobile US’s net profit nearly tripled in the fourth quarter after it added more than 2 million customers.
Last year it overtook Sprint to become the third largest provider.
An attempt to sell T-Mobile to Sprint in 2014 was blocked by US regulators and last year talks between T-Mobile US and Dish Network Corp stalled.
Deutsche Telekom has always said it was under no pressure to sell but that it would consider any offer.
Deutsche Telekom shares pared gains to stand 0.2% higher at 1429 GMT.