WASHINGTON — The Trump administration’s push to deliver long-promised criminal justice and prison sentencing reform will have to wait until after the midterm elections, according to multiple officials familiar with meetings held Thursday.

The timing is caught up in tensions between the president and his attorney general, Jeff Sessions, and the backdrop of midterm politics.

In a new development, a senior administration official told NBC News that Senate Majority Leader Mitch McConnell, R-Ky., agreed to a formal count of GOP members to assess support for the legislation — after the election.

Sens. Chuck Grassley of Iowa, a Republican, and Dick Durbin of Illinois, a Democrat have been fighting for years for a sweeping set of changes that would target the source of mass incarceration by reducing sentences for nonviolent offenders. A third of the Senate's membership have signed on as co-sponsors.

Although the White House had hoped for consideration as soon as possible, including before November, that timing slipped away Thursday.

“I think it would have been good politics, but I think that McConnell now doesn’t want the headache,” an official said.

The White House described McConnell’s view as “if you have a strong whip count but a few vocal critics after the election, then I’ll care less about the vocal critics then.”

The administration framed the timing as an opportunity. “That gives us a couple months to get everyone together to dispel some of the misinformation that’s been put out about it,” the senior administration official said.

McConnell’s office responded, “The Leader made clear there will be no vote on this legislation during the pre-election work period. And while no commitments were made by the Leader on holding a vote, proponents of the legislation will continue to discuss the issue with their colleagues followed by a whip count after the October session to accurately assess the Conference’s view on the issue.”

Some of the tension is brewing within the administration.

Sessions, who Trump attacked in an interview broadcast earlier Thursday, was part of a meeting with the president, and a source familiar with his position said delaying the bill was an “unequivocal win” for Sessions.

The attorney general is described as thinking it's “the wrong time for this,” the official said.

The Department of Justice said in a statement that, “We’re pleased the president agreed that we shouldn’t support criminal justice reform that would reduce sentences, put drug traffickers back on our streets and undermine our law enforcement officers who are working night and day to reduce violent crime.”

Sessions is described by senior White House officials as “supportive” of the legislation while they acknowledged that the attorney general “had heartburn on the safety valve expansion,” which would give judges more discretion on sentencing for low-level crimes.

Officials declined to discuss whether current tension Trump and Sessions, who pushed back against the president in a rare move Thursday, is an obstacle for the legislation. “I think it was a constructive discussion and it wasn’t one arguing versus the other," an official said. "It was more just discussing the substance and the president asking a lot of questions.”

Trump supported revisions, including some offered by Durbin, according to officials who said the president “was trying to reconcile those changes with kind of the fear mongering that was being spread.”

The meetings included the president, senior adviser and Trump son-in-law Jared Kushner, McConnell, Judiciary Chairman Grassley, and Sens. John Cornyn and Mike Lee. who described the Thursday discussion as a “huge step forward.”

“I’m very encouraged by the leadership shown today by President Trump to make prison and sentencing reform a priority soon after the election and Leader McConnell’s openness to bring it up this year," Grassley said. And I’m confident with the president’s continued backing, we’ll have more than enough votes to pass a bill overwhelmingly."

A recent poll shows that Americans overwhelmingly support prison and sentencing reforms

The White House contends the reform policies could ultimately attract broader appeal.

“A lot of the people who were against, are actually for it this time because it’s a better bill,” said a senior administration official.

However, prominent critics remain, such as Sen. Tom Cotton, of Arkansas, who had pressed the president to hold off and called the plans a “jailbreak” for offenders.