U.S. Assistant Attorney General for Antitrust Makan Delrahim testifies before the Senate Judiciary Committee during an oversight hearing on the enforcement of antitrust laws in the Dirksen Senate Office Building on Capitol Hill October 03, 2018 in Washington, DC.

The Justice Department remains open to the $26.5 billion merger of T-Mobile and Sprint despite reports that it was leaning toward rejection, sources told CNBC's Andrew Ross Sorkin.

Makan Delrahim, head of the DOJ's antitrust division, is still talking with the companies and may be trying to find a way to support a deal despite his staff's opposition, the sources said.

Discussions about possible remedies are ongoing. But what kind of remedies — beyond what the companies committed to as part of a deal with the Federal Communications Commission — remain unclear.

Shares of Sprint jumped 4.6% in Thursday's premarket following Sorkin's report. T-Mobile shares were up nearly 1%.

Earlier this week, FCC Chairman Ajit Pai, elevated to the top post by President Donald Trump in 2017, said he plans to recommend his agency approve the merger after the companies committed to not raising prices for three years.

It's possible, according to Sorkin's reporting, that the DOJ could push for more years on no price hikes, for example.

The Obama administration rebuffed earlier efforts by the companies to merge, as well as an attempted deal between AT&T and T-Mobile, on concerns that such deals would hurt competition in the wireless industry.

— AP contributed to this report.