AMNA NAWAZ: Trump administration officials briefed members of Congress today on the war with Iran.

That's as both chambers gear up to vote on a War Powers Act that could limit President Trump's authority in carrying out strikes.

To discuss that, I'm joined by Senator Mark Warner of Virginia.

He is the top Democrat on the Senate Intelligence Committee.

Senator Warner, welcome back to the "News Hour."

Thanks for being with us.

SEN.

MARK WARNER (D-VA): Thank you so much.

AMNA NAWAZ: So you were briefed today with all the other senators, yesterday as part of a smaller group in the Gang of Eight.

Were you given any evidence in either of those briefings that showed Iran was an imminent threat to the U.S., to U.S.

military assets in the region, or to U.S.

allies?

SEN.

MARK WARNER: Absolutely not.

This is a war of choice brought by Donald Trump.

In many ways, and I say this is a strong supporter of Israel, the timing of this war was dictated by Bibi Netanyahu.

And while I support Israel, I think at the end of the day, when American interests were at stake, when we have lost six soldiers at this point, we have to show the direct support and immediate risks to America.

That was not the case.

And we have seen now over the last week or so, and I have been in every one of the classified briefings, there have been now four reasons given for why this war was started.

One was to take out Iran's nuclear capabilities that the president claimed was eliminated nine months ago.

Then it was moved to the ballistic missiles, which was a rising threat against American bases in Israel, but not imminent.

Yesterday, we even heard an answer about getting rid of the Iranian navy.

We have never heard that before.

And then we have heard from the president regime change.

And, as your prior reporter indicated, Iran's a complicated company of -- a country of 92 million people.

If the president has called upon the Iranian people to rise up, and let's say in a few days 100,000 Iranian protesters go to the street and the Iranian military kills 5,000, 10,000, 20,000, does the United States have any obligation to do anything?

So we are in a war of choice where we don't know what success will be viewed as, and we don't know what the next steps will be.

AMNA NAWAZ: Let me ask you more about the protesters in just a moment.

But in terms of the long-term goal here we have heard articulated in various forms by the administration, if it is to prevent a nuclear-armed Iran, a regime that is hostile to the U.S.

and hostile to its allies, hostile to its own people, as you mentioned, the tens of thousands protesters is killed, is that a goal that is worth it in the long run to try to take out this regime?

SEN.

MARK WARNER: Well, I had -- I shed no tears for the death of the supreme leader and the Iranian leadership, who have American blood and other blood on their hands.

But the thing is, if the president had chosen to try to take an action like this in January, when the Iranian people were on the streets by the millions, I would have been more sympathetic or at least listened to his case.

He couldn't do it at that point for two reasons.

One, the military capability that we needed in the region, the aircraft carrier the Ford that is home-ported in Norfolk, Virginia, was off the coast of Venezuela on another one of his military follies.

And then the ability to have our European allies help us, who also don't want Iran to have a nuclear capability, they were occupied because of Trump's, I think, folly of trying to go after Greenland.

So he chose -- he couldn't act then.

He's now built up these forces for months on end, acted not because of an immediate threat, but in concert with our ally Israel, which is an ally.

But if they had all this time to plan, where in the heck are the plans to get rid of the literally hundreds of thousands of Americans who are now caught in a war zone with no way out?

AMNA NAWAZ: Senator, if I may, part of the reasoning we heard today from the administration was that this is an Iran that was weakened in a way that it wasn't before and that was part of the timing, they say.

But, to your point, if we are where we are now, if people in Iran do take to the streets, will and should the U.S.

support them in a way that they haven't before?

What would you like to see happen now?

SEN.

MARK WARNER: Well, let me answer your first question.

Iran is weakened.

And that is a good sign.

But Iran was not going to be stronger a month from now if those negotiations were to appear that there might have been some breakthroughs.

Why not let the negotiations follow through a little bit?

Then we could have maybe rallied more of the world to our side if Iran was not willing to make concessions.

AMNA NAWAZ: But should the U.S.

support protesters now?

Would you like to see that happen?

SEN.

MARK WARNER: Now the very real question is, if the Iranian people go to the street because the president has called them to the street, I am very reluctant and I don't think the American people want to put American troops on the ground.

But you can't protect those protesters from the air.

And what I fear is happening -- and let me be the first to acknowledge I'm a Democrat, but I think our exit from Afghanistan in many ways was a disaster.

I think we are now seeing in Trump's war of choice the beginnings of what could be even more disastrous about how we protect our interests in the region, how we protect our allies in the region who are now being hit, and actually how we actually do something for the Iranian people.

AMNA NAWAZ: Senator, we have got 30 seconds left.

I have to ask you.

You said you would support a War Powers Act that could be voted on as early as tomorrow.

Yes or no, does that have the support to pass?

SEN.

MARK WARNER: I would hope so.

But I am so, frankly, frustrated with my Republican friends who constantly say, "Oh, Mark, you're right, you're right, you're right," but never have the courage to vote.

If we don't at some point say the president of the United States has to follow the Constitution, then I'm not sure where we're headed.

AMNA NAWAZ: That is Senator Mark Warner of Virginia joining us tonight.

Senator Warner, thank you.

Good to speak with you.

SEN.

MARK WARNER: Thank you.

AMNA NAWAZ: And a note that, tomorrow night, we will speak to Republican Senator Katie Britt of Alabama.