Sessions, who held his Senate seat for 20 years, declined to comment on questions about his plans, an assistant said.
Within days of leaving the Justice Department in November, Sessions was discussing with close friends and advisers whether he should attempt to return to the Senate.
After months of such conversations, it is still unclear which way the 72-year-old Sessions is leaning, according to people familiar with the discussions who spoke on the condition of anonymity to share private conversations.
Friends of the former attorney general have raised a number of factors that could affect his decision, including his general popularity in his home state, his age, whether he is up for the rigors of campaigning and whether his falling out with President Trump could harm a Senate candidacy, according to people familiar with the discussions.
While many have encouraged Sessions, some have also warned that running anew for office will be harder than seeking reelection, particularly given Moore’s expected candidacy.
Shelby’s comments came a day ahead of a planned announcement by Moore in Montgomery, Ala., about whether he will run again.
Moore, who fell short in a special election two years ago amid allegations of sexual misconduct with teenage girls in the 1970s, has been eyeing a rematch next year with now-Sen. Doug Jones (D).
Moore has repeatedly hinted he will enter the race despite misgivings expressed by Trump and numerous other high-profile Republicans.
In a tweet last month, Trump stood by his support for Moore in 2017 but warned that a second loss would give Jones the Senate seat for six years as opposed to the two-year term he won in the special election to replace Sessions.
Responding to Trump, Moore asked in a tweet why he “scares the ‘hell’ out of the Washington DC establishment.”
An advisory issued by Moore on Wednesday said he would make “an official announcement regarding his plans for the Alabama senate race” on Thursday afternoon at an event with guests. Moore indicated he would take questions from the news media after his announcement.
Shelby said Wednesday he would not support Moore, a former chief justice of the Alabama Supreme Court, for the Senate seat.
“There are a lot reasons known to you and everybody else,” Shelby said. “I think Alabama could do better. I think he would be a disrupter . . . I won’t be supporting him.”
Shelby suggested it would be difficult to beat Jones next year if Moore is the GOP nominee.
“I think we’ve got a lot of talent in Alabama that maybe could come to the front,” he said.
Several Republicans have already announced bids, including Rep. Bradley Byrne; Alabama Secretary of State John Merrill; state Rep. Arnold Mooney; and former Auburn University football coach Tommy Tuberville.
Sessions resigned from the Senate in 2017 to join Trump’s Cabinet as attorney general.
Trump repeatedly and publicly berated Sessions for recusing himself from the investigation into Russian interference in the 2016 presidential election. Sessions, who was a high-profile supporter of Trump’s 2016 campaign, resigned as attorney general in November at Trump’s request.