WASHINGTON (AP) — Russia's war on Ukraine has most Americans at least somewhat worried that the U.S. will be drawn directly into the conflict and could be targeted with nuclear weapons, with a new poll reflecting a level of anxiety that has echoes of the Cold War era.

Close to half of Americans say they are very concerned that Russia would directly target the U.S. with nuclear weapons, and an additional 3 in 10 are somewhat concerned about that, according to the new poll from The Associated Press-NORC Center for Public Affairs Research. Russian President Vladimir Putin placed his country's nuclear forces on high alert shortly after the Feb. 24 invasion.

Roughly 9 in 10 Americans are at least somewhat concerned that Putin might use a nuclear weapon against Ukraine, including about 6 in 10 who are very concerned.

"He is out of control, and I don't think he really has concern for much of anything but what he wants," said Robin Thompson, a retired researcher from Amherst, Massachusetts. "And he has nuclear weapons."

Seventy-one percent of Americans say the invasion has increased the possibility of nuclear weapons being used anywhere in the world.

The poll was conducted before North Korea test-fired its biggest intercontinental ballistic missile on Friday but also shows 51% of Americans saying they are very concerned about the threat to the U.S. posed by North Korea's nuclear program. An additional 29% expressed moderate concern.

Fear of nuclear war has been a fact of life for decades. The Bulletin of the Atomic Scientists has published its "Doomsday Clock" since 1947, showing a theoretical countdown to nuclear annihilation. The latest update, in January, put the time at 100 seconds to midnight — unchanged since 2020, but still closer than ever to Armageddon.

It's difficult to measure the public's degree of fear over time because polls use different methodologies or pose questions in different ways. Alex Wellerstein, a nuclear historian at the Stevens Institute of Technology in New Jersey, said people often won't bring it up on their own but list it among concerns if given the choice.

The fear, naturally enough, also tends to rise and fall depending on what is happening around the world. "We have these moments that are sort of high crisis periods," Wellerstein said. "And then they come and go, and people forget that we had them."

One particularly high point, he said, was in 1983, a time of tension between the U.S. and the Soviet Union and the year that a highly watched movie about nuclear war, "The Day After," first aired on TV in the United States.

In the recent AP-NORC poll, close to half of Americans say they are "extremely" or "very" concerned that the U.S. might be drawn into a war with Russia. Roughly 4 in 10 Americans said they are "somewhat" concerned.

The findings reflect not just anxiety about what seems like a proxy war with Russia, even if the U.S. isn't directly involved in the conflict, but also the unprecedented saturation coverage of the war through traditional news outlets and social media.

"We are seeing almost moment by moment what's happening to these poor people," said Linda Woodward, a retired phone company technician from Hot Springs Village, Arkansas.

The concern about nuclear war cuts across party lines and even resonates with some young adults who were born after the Cold War.

Caleb Pack, a 21-year-old Republican from Ardmore, Oklahoma, was among those who said that they were "somewhat concerned" that the U.S. would be drawn into the war and that Russia would target the United States with nuclear weapons.

"If Russia's end goal is to reclaim Soviet Union territory, that means they're going to push into NATO countries, which obviously I think could escalate very quickly," said Pack, who works in information systems.

Certainly, Russia hasn't taken steps to alleviate concerns. Putin issued what appeared to be an ominous threat when he reminded the world in a speech the day he launched the invasion that his country is "one of the most powerful nuclear states."

In that context, concern is justified, said Tara Drozdenko, director of the global security program at the Union of Concerned Scientists. "Whenever you have nuclear-armed nations getting closer to conflict, there's always a risk of nuclear escalation," she said.

So far, NATO and the Biden administration have been careful not to escalate the situation, Drozdenko said. But she believes the public should use this time to push for changes to limit the risk. That would include adopting a formal policy that the U.S. would not strike first with nuclear weapons, to reduce the risk of an accidental strike by an adversary, and taking the final authority for a launch out of the hands of the president alone.

Historian Wellerstein also sees a possible upside to the heightened state of concern. He cited research showing that a crisis can have the long-term effect of getting people more engaged with an issue.

"This thing with Ukraine will inevitably end, hopefully sooner rather than later," he said. "This could be an opportunity for getting a lot more people, especially younger people, invested in this as a political issue."

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The AP-NORC poll of 1,082 adults was conducted March 17-21 using a sample drawn from NORC's probability-based AmeriSpeak Panel, which is designed to be representative of the U.S. population. The margin of sampling error for all respondents is plus or minus 4.0 percentage points.