BEDMINSTER, N.J. — President Trump escalated his attacks on Saturday against his attorney general, Jeff Sessions, describing him as “scared stiff” by an issue related to the Russia investigation that the president has privately railed to his aides has received insufficient news coverage.

Mr. Trump’s latest broadside included some of his harshest language yet against Mr. Sessions, whom the president begrudges for recusing himself from the Justice Department’s investigation into possible collusion between the Trump campaign and Russian officials in 2016.

“I have never seen anything so Rigged in my life,” Mr. Trump wrote on Twitter, referring to reports about meetings between a Justice Department official and a former British spy who helped compile a dossier that contained unverified but potentially damaging allegations about Mr. Trump. “Our A.G. is scared stiff and Missing in Action.”

The reports, featured mostly in conservative news outlets, suggest that even after the Justice Department stopped using the former spy, Christopher Steele, as an informant, he continued to meet with a top official at the agency, Bruce Ohr.