Sen. Martin Heinrich, D-N.M., on Tuesday accused Attorney General Jeff Sessions of "obstructing the congressional investigation" into Russian meddling in the 2016 election by not answering questions about his conversations with President Trump.

"There are two investigations here. There is the special counsel investigation. There is also a congressional investigation. And you are obstructing that congressional investigation by not answering these questions, and I think your silence, like the silence of Director Coats, like the silence of Admiral Rogers, speaks volumes," Heinrich said Tuesday, referring to Director of National Intelligence Dan Coats and National Security Agency Director Mike Rogers.

Both Coats and Rogers testified before the Senate Intelligence Committee last week on Russian meddling in the 2016 election and declined to disclose the details of private conversations they had with Trump.

Sessions followed suit during his own testimony before the intelligence panel and said it would not be appropriate for him to discuss his private conversations with the president.

"It is my judgment it would be inappropriate for me to answer and reveal private conversations with the president when he has not had a full opportunity to review the questions and make a decision on whether or not to approve such an answer," the attorney general said.

Trump did not invoke executive privilege to keep Sessions from sharing the details of his conversations, but Sessions still declined to provide information regarding their discussions.

Republicans like Sen. James Lankford, R-Okla., later reminded Democrats that former Attorney General Eric Holder routinely said he would not describe private conversations with President Obama.

But Heinrich and other Democrats took issue with that answer.

"You took an oath. You raised your right hand here today and said you would solemnly swear to tell the truth, the whole truth and nothing but the truth, and now you're not answering questions. You're impeding this investigation," Heinrich said. "My understanding of the legal standard is that you either answer the question. That's' the best outcome. [Or] you say this is classified, can't answer it here, I'll answer it in closed session. That's bucket number two. Bucket number three is to say I'm invoking executive privilege. There is no appropriateness bucket. It is not a legal standard."

Sessions, though, said he was "protecting the president's constitutional right" by not testifying about his discussions with Trump.

"I am telling the truth in answering your question in saying it's a longstanding policy at the Department of Justice to make sure the president has full opportunity to decide these issues," he said.