AMNA NAWAZ: In cryptic remarks today, President Trump wouldn't say whether he's willing to join Israel in its attempt to destroy Iran's nuclear program.

GEOFF BENNETT: But, according to The Wall Street Journal, President Trump told senior aides he has approved of attack plans, holding off only to see if Iran changes course.

The prospect of direct U.S. involvement has added to fears of a wider war in the Middle East.

Tonight, cities in Israel and Iran under fire, the countries at war trading more blows overnight and into today, nearing a week of strikes in the ever-depending conflict.

And here at home... DONALD TRUMP, President of the United States: You don't seriously think I'm going to answer that question.

GEOFF BENNETT: ... the major question still unanswered tonight, whether President Trump would push the U.S. into the conflict and join Israel's strikes on Iranian nuclear facilities.

DONALD TRUMP: You don't know that I'm going to even do it.

You don't know.

I may do it.

I may not do it.

I mean, nobody knows what I'm going to do.

I can tell you this, that Iran's got a lot of trouble.

We will see.

The next week is going to be very big, maybe less than a week, maybe less.

GEOFF BENNETT: President Trump, speaking with reporters as workers installed new flagpoles on the White House South Lawn, said Iran had reached out to him and even proposed coming to the White House for talks.

QUESTION: Mr. President, have you given the Iranians an ultimatum?

DONALD TRUMP: You could say so, right?

They know what's happening.

Maybe you could go with the ultimate, the ultimate ultimatum, right?

GEOFF BENNETT: Meantime, the death toll in Iran is mounting.

The U.S.-based Iranian human rights group says more than 200 civilians have been killed in Israel's strikes.

But, for its part, Iran sought to project strength today, with its supreme leader rejecting President Trump's call for unconditional surrender.

AYATOLLAH ALI KHAMENEI, Supreme Leader of Iran (through translator): The Americans, those who are familiar with the politics of this region know that the damage America will suffer if it makes a military intervention in this field will undoubtedly be irreparable.

GEOFF BENNETT: If the U.S. decides to join Israel in its attack on Iran, one main target would be the Fordow nuclear enrichment site southwest of Tehran.

Built deep into a mountain, the facility appeared unscathed in recent satellite imagery taken after Israel's latest strikes.

To penetrate and destroy that facility, experts say it would require so-called bunker-buster bombs carried aboard B-2 bombers, both of which the U.S. has and Israel does not.

But entering the fight could alienate a part of Mr. Trump's base, those who are against engaging the U.S. in new foreign wars, among them, Tucker Carlson, who recently sparred with Senate Republican Ted Cruz on the prospect of regime change in Iran.

TUCKER CARLSON, Former FOX News Anchor: You don't know anything about Iran.

So, actually, the country... SEN. TED CRUZ (R-TX): OK, I am not the Tucker Carlson expert on Iran, who says... (CROSSTALK) TUCKER CARLSON: You're a senator who's calling for the overthrow of the government, and you don't know anything about the country.

GEOFF BENNETT: President Trump today insisted any action against Iran would have a clear end.

QUESTION: Some of the people in the base don't want a long-term war.

They're afraid that we're going to get into a long-term war.

DONALD TRUMP: We're not going to have a long-term war.

We're looking -- it's only -- I only want one thing.

Iran cannot have a nuclear weapon.

That's it.

I'm not looking long-term, short-term.

And I have been saying that for 20 years.

GEOFF BENNETT: Meantime, the U.S. has sent more military aircraft and warships to the region, staying prepared to defend Israel and American assets as the region awaits President Trump's decision.