At the end of a conversation with CNN's Candy Crowley on Sunday, Sen. Dianne Feinstein (D-Calif.) agreed with Crowley's bleak assessment of the relationship between the United States and Russia: Yes, she said, the two countries are at Cold War levels of tension.

Feinstein, who chairs the Senate Intelligence Committee, appeared on "State of the Union" and largely reinforced Secretary of State John Kerry's assessment of the aftermath of the crash of Malaysia Airlines Flight 17.

There is a "nexus" between Russia and the separatist forces that the United States believes shot the plane down, she said, asking, "Where is Putin?" She continued, "I would say, 'Putin, you have to man up.'"

"You should talk to the world," she said. "If this was a mistake -- which I hope it was -- say it. Even if it was a mistake, it's a horrendous mistake to make. I think it points out the futility of what's happening in the Ukraine, because there will be repercussions from this."

"I think the world has to rise up and say, 'We've had enough of this,'" Feinstein said. "It's difficult, because you need Russian help in so many things: the P5+1, Syria. ... But you cannot let this kind of thing happen." Contrary to Sen. John McCain (R-Ariz.), who argued that the United States should better arm Ukraine's military to fight the rebels (who Feinstein called "in many respects, thugs"), Feinstein said: "I don't think you can win this that way. I think you can only win it diplomatically."

And at the end of the interview, the question from Crowley. "Do you believe that the U.S.-Russian relations are now at Cold War levels?"

Feinstein responded flatly. "Yes."