Sprint Corp. and T-Mobile US Inc. have restarted talks about a potential deal, according to people familiar with the matter, five months after efforts to combine two of the biggest U.S. wireless providers fell apart.

It's not clear exactly what terms the companies are discussing, said the sources, who asked not to be identified as the details aren't public. Previous discussions to merge the carriers collapsed in November after months of negotiations as executives tussled over how control of the combined entity could be shared, people with knowledge of the talks said at the time.

The sort of issues that led to the deal falling apart last time haven't been resolved in the interim, one of the people said.