Sen. Tim Kaine, D-Va., said Tuesday the ongoing Russia investigation should move beyond issues concerning obstruction of justice and into potentially treasonous acts after news emerged that Donald Trump Jr. met with a Kremlin-tied lawyer last year.

Kaine told reporters that while there is no proof of any legal wrongdoing, the investigation into potential ties between the Trump campaign and the Russians has become a "treason investigation."

"Nothing is proven yet. But we're beyond obstruction of justice in terms of what's being investigated," Kaine said. "This is moving into perjury, false statements, and even into potentially treason."

"To meet with an adversary to try to get information to hijack democracy. The investigation is now more than just obstruction of justice in investigation. It's more than just a perjury investigation. It's a treason investigation," the 2016 Democratic vice presidential nominee continued.

"We don't know the answer to the question yet. An investigation is not that same as ultimately something that's going to lead to charges but that's what this investigation is."

Kaine's comments come a day after the New York Times reported Trump Jr. received an email warning him potential material being floated to him to harm Hillary Clinton's campaign was part of the Russian government's push to aide his father's campaign.

Initially, Trump Jr. said the meeting with Russian lawyer Natalia Veselnitskaya was to discuss Russian adoption in the U.S., which Russian President Vladimir Putin put an end to due to the Magnitsky Act putting sanctions on Russian human rights abusers. But, the Times reported on Sunday that Trump Jr. was under the impression Veselnitskaya had potentially damaging information on Clinton.

Trump Jr. said Monday he is willing to meet with any potential committees on Capitol Hill to talk about the meeting.