Under a fresh cloud of overseas violence, Donald Trump and Hillary Clinton fought to extend their delegate leads in primary voting across three Western states on Tuesday as the 2016 presidential contest turned into a clash of would-be commanders-in-chief.

The contests in Arizona, Utah and Idaho were largely an afterthought for much of the day as the world grappled with a new wave of bloody attacks in Europe. The Islamic State group claimed responsibility for a series of blasts in Brussels that left dozens dead and many more wounded.

As voters cast ballots, the presidential candidates lashed out at each other's foreign policy prescriptions, showcasing sharp contrasts in confronting the threat of Islamic extremism.

Trump, the Republican front-runner, charged that the United States has "no choice" but to adopt his proposed temporary ban on Muslims entering the country to prevent the spread of terrorism. He described as "eggheads" those who respect international law's ban on torture, the use of which he argued would have prevented the day's attacks.

"We can be nice about it, and we can be politically correct about it, but we're being fools," Trump said in an interview on CNN. "We're going to have to be very strong, or we're not going to have a country left."

Clinton and Trump's Republican rivals, meanwhile, questioned the GOP front-runner's temperament and readiness to serve as commander in chief, and condemned Trump's calls to diminish U.S. involvement with NATO.

"I see the challenge ahead as one where we're bringing the world together, where we're leading the world against these terrorist networks," Clinton said Tuesday at a union hall in Everett, Washington. "Some of my opponents want to build walls and shut the world off. Well, you tell me, how high does the wall have to be to keep the Internet out?"

Texas Sen. Ted Cruz seized on Trump's foreign policy inexperience while declaring that the U.S. is at war with the Islamic State group.

"He doesn't have the minimal knowledge one would expect from a staffer at the State Department, much less from the commander in chief," he told reporters. "The stakes are too high for learning on the job."

Trump and Clinton both enjoyed overwhelming delegate leads heading into Tuesday's contests. Arizona and Utah featured elections for both parties, while Idaho Democrats also held presidential caucuses.

Democrat Bernie Sanders and Republicans Cruz and John Kasich hoped to reverse the sense of inevitability taking hold around both party front-runners. Anti-Trump Republicans are running out of time to prevent him from securing the 1,237 delegates needed to claim the nomination.

With more than half of all delegates already awarded during the first seven weeks of primary voting, Trump's challengers' best — and perhaps only — hope lies with denying the front-runner a delegate majority and forcing a contested national convention in July.

On the Democratic side, Clinton's delegate advantage is even greater than Trump's.

The former secretary of state is coming off last week's five-state sweep of Sanders, who remains popular among his party's most liberal voters but needs to improve his performance if he expects to stay relevant. The Vermont senator, now trailing Clinton by more than 300 pledged delegates, has targeted Tuesday's races as the start of a comeback tour.

Sanders condemned his GOP rivals' calls for stepped up surveillance of Muslims in the United States.

"That would be unconstitutional — it would be wrong," he told reporters during an appearance in Flagstaff, Arizona.

The underdogs in both parties had reason for optimism Tuesday.

Trump's brash tone has turned off some Republican voters in Utah, where preference polls suggest Cruz has a chance to claim more than 50 percent of the caucus vote — and with it, all 40 of Utah's delegates. Trump could earn some delegates should Cruz fail to exceed 50 percent, in which case the delegates would be awarded based on each candidate's vote total.

Trump appears to be in a stronger position in Arizona, which will award all of its 58 delegates to whichever candidate wins the most votes.

Kasich hopes to play spoiler in Utah, a state that prizes civility and religion.

A week ago, the Ohio governor claimed a victory in his home state — his first and only win of the primary season. Kasich on Tuesday criticized his Republican opponents for targeting Muslims in their responses to the Brussels violence.

He told reporters in Minnesota he doesn't believe all Muslims in Minnesota or elsewhere are "somehow intent on trying to destroy our families." He said, "This is a time when you have to keep your cool."

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Associated Press writers Catherine Lucey in Everett, Washington, Jonathan Lemire in New York and Jill Colvin in Washington contributed to this report.

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