In a statement, Mr Sessions said: “I never met with any Russian officials to discuss issues of the campaign. I have no idea what this allegation is about. It is false.”

He followed up with an interview on MSNBC on Thursday morning, when he hinted he might stand aside from the investigation.

"I have said that, when it's appropriate, I will recuse myself," he said.

His denial hinges on whether his contacts were part of his routine activities as a senator or his role as senior adviser to Mr Trump’s campaign.