The German carrier also wants Sprint to pledge to keep the T-Mobile brand and some of its management.
Deutsche Telekom's demands come after regulators implied they would view any Sprint/T-Mobile tie-up skeptically. Three years ago, Deutsche received $3B when authorities blocked the sale of T-Mobile to AT&T.
The sides are working on forging a deal in the near term, but could wait until after a government auction of wireless airwaves - which is expected in 2015 - or under a different White House administration.
The operators might have a bit more clarity next week, when the FCC is due to decide on how much spectrum carriers can hold and the rules for the spectrum auction.