'No magic fix' on North Korea, expert says

A North Korea expert said it's clear we need more sanctions against North Korea, but fears that President Donald Trump's earlier threat to "totally destroy" the rogue nation if it attacks the U.S. or its allies will backfire.

"We clearly need more sanctions. It's good to have more sanctions. But we've been sanctioning Korea for years now. There's no magic fix here," Joe Cirincione, president of the Ploughshares Fund, a global security foundation based in Washington D.C., told ABC News.

Trump unveiled new economic sanctions against North Korea Thursday that target the regime and companies that do business with them.

"In the end you can't sanction North Korea into collapse or compliance. You're going to need a negotiated solution," Cirincione said.

"The United States has great strength and patience, but if it is forced to defend itself or its allies, we will have no choice but to totally destroy North Korea," Trump said at the United Nations General Assembly Tuesday.

That language was "way over the top and extremely unhelpful," according to Cirincione. "You have just given North Korea the propaganda coup of the century. This is exactly what the North Korean regime is telling its people - that you need a strong leader, you need a nuclear program in order to protect yourselves from the United States."

Cirincione predicted that Trump's tough tone will only encourage North Korean leader Kim Jong Un to carry out more of the nuclear and missile tests that have so alarmed the world. He did however praise the president for expanding sanctions against the North, and for his role in pressuring China to impose new banking restrictions.

But without negotiations, Cirincione predicted that North Korea will not slow down its nuclear program, and could have as many as 100 nuclear-tipped missiles with the next five years.

"There is no way North Korea is going to give up its weapons right now. They look at Iraq, they look at Libya, and the lesson they draw is that if you give up your weapons America is going to kill you," said Cirincione. "That's not irrational. That's realist."