Chiefs at SoftBank and Deutsche Telekom must conclude a Sprint/T-Mobile US merger saga before an upcoming spectrum auction and potential change in the regulatory environment in the US threaten to put the deal on ice again, Reuters reported.

The news website’s sources said the companies would not get a better chance to clinch a tie-up, but it must be struck prior to the opening of the Federal Communications Commission’s (FCC) mmWave spectrum auction, provisionally slated for November.

Once such regulatory actions are in progress, all market activity talks (including M&A discussions) between participants are put on hold. The same policy delayed previous discussions between the two in Q1 2017: at the time, the FCC was midway through auctioning old broadcast spectrum for use by mobile operators.

The FCC’s mmWave auction will take some time to complete and could change the dynamics of a deal as the operators are likely to make different levels of financial commitment.

Reuters’ sources also raised the suggestion Sprint could struggle to handle the costs of building out the new network on its own given its current financial position.

Waiting until the end of the auction process could also introduce further regulatory uncertainty for any deal, Reuters sources added. Given the length of time other large mergers have taken to get the green light, it may conclude after the 2020 US election and a subsequent change in the regulatory landscape.

Media reports raising the prospect of a deal to merge Sprint and T-Mobile US appeared earlier this week and follow two abandoned attempts from parent companies SoftBank and Deutsche Telekom to strike a deal.