This story has been updated.

ROCK HILL, S.C. -- Republican presidential candidate Jeb Bush declined to say on Tuesday whether GOP front-runner Donald Trump is qualified to be commander in chief, but he urged his rival to speak more substantively about national security.

Bush appeared Tuesday morning at Winthrop University for a national security forum hosted by Americans for Peace, Prosperity and Security, an organization led by a cadre of Republican foreign policy and national security experts. For more than an hour, he fielded questions on his plans to combat the Islamic State terror group, how he would work with China and Russia and whether women should be allowed to serve in combat.

Afterward, he was asked whether Trump is qualified to deal with such issues.

"I’m going to focus on my candidacy and my experience and my views and let others -- I hope that 'Secretary Trump' takes advantage of APPS to have a sit-down conversation and have a detailed conversation about things of substance," he said. "That’s what Americans want in the end, that’s what I’m going to focus on. I’ll let others judge peoples’ qualifications." It was not immediately clear why Bush referred to the real estate mogul as "Secretary Trump."

A Bush aide later denied that the reference had been a dig at Trump, saying that the former Florida governor had just answered a question about former secretary of state and current presidential candidate Hillary Clinton, and accidentally conflated the two in his next response.

The former Florida governor began the year at the top of the Republican pack but has slipped back in national and early-state primary polls as Trump has surged into the lead. Others, including Ohio Gov. John Kasich, are now closely trailing Bush after beginning their campaigns much later in the year.

In recent weeks, Bush has repeatedly declined to directly attack Trump or answer questions about the businessman's qualifications to serve as president, suggesting that GOP voters will ultimately settle such concerns. Bush does however raise questions about Democratic front-runner Hillary Rodham Clinton.

On Tuesday, he said in response to a question that Clinton's issues with her personal e-mail reflect a national security problem and a concern about her judgment.

"You have classified information going over a server that is against the law. It’s certainly against the policy of the administration that she served; that’s a problem," he said. "The fact that she’s not been forthright in explaining the situation is also a problem."

Bush also clarified comments he made to The Washington Post on Monday evening, when he said, "There are like 10 things I would change in the Constitution with a magic wand."

In fact, he said, he doesn't have 10 specific things he'd like to change about the Constitution.

"I said that there are all sorts of amendments – the balanced budget amendment – there’s all sorts of things that people can say as a candidate that you’d do, but the likelihood of those happening is really not a policy," he said. "They take a long, long time. I’d love to see a balanced budget amendment – in fact, that’s actually closer than many other ideas that people have about changing, amending the Constitution. But we need to start solving problems in advance of that."

Irked that reporters would suggest that he wants to make 10 changes to the Constitution, he added: "I mean, is there any way to actually have a conversation with people where the context of the words are clear?"

The candidate also said that he is opposed to ending birthright citizenship -- something that Trump has proposed as a way to deter illegal immigration and that another GOP presidential candidate, Wisconsin Gov. Scott Walker, said he supports.

"Look, this is a constitutionally protected right. I don’t support revoking it," he said. "That’s not one of my – I mean, look, there’s a way to use leadership to solve abuses for people that are coming into the country, having children so that their children can be citizens. That’s a legitimate problem, and there’s a targeted way you can deal with this issue. But to suggest that people born in this country are not United States citizens, that they don’t have this in the Constitution, I just reject out of hand."

During the forum, moderator Jeanne Meserve noted that two female soldiers are poised to graduate from the Army’s grueling Ranger School on Friday and asked Bush whether women should be allowed to serve in combat.

"Absolutely, if they’re Rangers, they’re clearly qualified," he said. "These decisions ought to be made by the military, not by the political side of life in Washington, D.C. But if you’re Ranger-ready, you’re combat-ready."

He also faulted President Obama yet again for failing to have a clear strategy on how to defeat the Islamic State.

"I want to win; I want to take them out," he said.

"We can’t do this alone. We can’t be the world’s policemen," he said. "What happens if we did that -- if we came in, we can take them, militarily we have the capability to do this, but immediately the chaos that would ensue would create another void. Just as it's done historically. Libya is a good example of this. This administration doesn’t have a strategy; they’re incremental in their approach, and the net result is that we have chaos."

Bush is scheduled to visit Atlanta later Tuesday for a fundraiser before traveling to New Hampshire for two days of campaign stops. He'll also visit Ohio on Friday.