Ryan added that lawmakers have seen "no evidence" to determine that associates of the Trump campaign colluded with Russian officials.
"If he himself is a subject of an investigation, of course he should [recuse himself.] But if he's not, I don't see any purpose or reason for doing this," Ryan told reporters Thursday.
Sessions, a Trump campaign surrogate, is under increasing pressure following a Washington Post report that he met twice with Russia's ambassador to the United States before the 2016 presidential election. The report appears to contradict his denial in confirmation testimony to the Senate. Sessions has said his conversation came as part of his duties as a former senator, not as a Trump campaign surrogate.
Asked about possible Trump campaign contacts with Russia during his January confirmation hearing, Sessions said he had "been called a surrogate a time or two in that campaign. He said he "did not have communications with the Russians" and was unable to comment on alleged contacts between Trump campaign officials and Russian officials.
Ryan broke with several top Republican lawmakers and numerous Democrats who have said Sessions should distance himself from Russia-linked investigations. Still, most Republicans have either stayed mum on Sessions or defended his ability to act independently unless a probe relates to him directly.
Sessions oversees the Justice Department and FBI, which have led investigations into alleged Russian meddling in the election and any links between Russia and Trump associates. Sessions told NBC on Thursday that he will recuse himself "whenever it's appropriate," but did not say he will distance himself from Russia-related investigations specifically.
Ryan noted that the House and Senate intelligence committees are still investigating the extent of Russia's influence on the 2016 presidential election and argued the probes are best served staying within the committees. He said Democrats are "lighting their hair on fire" over the issue, following Senate Minority Leader Chuck Schumer and House Democratic Leader Nancy Pelosi's calls for Sessions to resign.
On Thursday, House Oversight and Government Reform Committee Chairman Jason Chaffetz told MSNBC he thinks Sessions should recuse himself from Russia-related investigations.
"Based on what we've read — and the information is not complete — I think the attorney general should further clarify and I do think he's going to need to recuse himself at this point," the Utah Republican said. He added that he came to his conclusion because of how Sessions answered questions in his testimony.
GOP Sens. Lindsey Graham and Rob Portman, of South Carolina and Ohio, respectively, also said it would be best if Sessions recused himself from Russia-related probes.