"The prospect of the North Koreans actually denuclearizing is near zero," said Michael Hayden, a former head of the CIA and the NSA. "They are not irrational in this regard, they've seen what happens to states who have given up their nuclear programs and they're trying to hold on to this as a matter of regime survival."

Adam Mount, a senior fellow at the Federation of American Scientists, told CNN he was particularly concerned that Trump sees North Korea giving up its nuclear weapons as a starting point, not an end of the negotiating process.

"He held to the same old insistence on complete, verifiable denculearization, without a plan to get there, which we didn't hear," Mount said. "That insistence will prevent any kind of forward progress."

The audiences

Though Trump stood before South Korean lawmakers, his audience was likely more global.

That may have not gone over well in the National Assembly chambers, where many politicians are concerned about the potential of a catastrophic conflict.

"Trump refrained from making really aggressive military threats and that will be appreciated in Seoul. The text of his speech really illustrated the historical and moral struggle going on on the Korean Peninsula, sometimes in very evocative terms. I think the Korean people will appreciate that too," said Mount.

"But the reality tonight is that we didn't get anything different from a strategic patience," he said, referring to President Barack Obama's North Korea policy that the Trump administration has declared is over.

James Clapper, the former US Director of National Intelligence, described the speech as "mostly stick and not much carrot."

Clapper called the speech "strong" and said he didn't believe it was likely to intimidate the North Koreans, but was surprised by the laundry list of human rights abuses.

"I wished he'd expanded more in his press conference remarks about a deal and offered something, a path to negotiation," he told CNN.

But Victor Cha, a former US diplomat involved in the six party talks and a rumored pick for the next US ambassador to South Korea, said on Twitter those expecting a public airing of the administration's plans shouldn't hold their breath.

"I would not expect a US president to lay out specific quid pro quos in a public speech," Cha tweeted. "He sent a direct public message to KJU (Kim Jong Un), for diplomacy, which is more than anyone would have expected."

Though Trump avoided the fiery rhetoric and name-calling that he's employed when previously discussing North Korea and its leader, Kim Jong Un, the address will likely still rub Pyongang's most powerful the wrong way.

He called life in the hermit nation "a hell that no person deserves" and said the country has committed crimes "against God and man."

"You don't go so overboard in insulting and attacking your adversary if you want to get into some kind of negotiation," said John Delury, a professor at Yonsei University's Graduate School of International Relations.

"It's one thing to bring human rights into the equation. It's another to spend the majority of the speech detailing the brutality of the North Korean state," Delury told CNN on the phone from Seoul after attending the speech. "What the South Koreans were looking for in the speech is reassurance that Trump will be moderate and that the alliance is strong but he's not going to precipitate military action."

After listing alleged abuses committed by the North Korean regime, Trump questioned why nations would continue to support Pyongyang. It was likely an implicit stab at Beijing, the next stop on the US President's nearly two week-long trip.

China accounts for about 90% of North Korea's trade, a vital lifeline for North Korea's small and sealed-off economy.

"Messaging to the Chinese and the Russians about severing relationships, I'm not sure what that means," said Clapper, the former US Director of National Intelligence.

"The Chinese are going to be hard-pressed to do that. The greater strategic imperative for the Chinese is that North Korea not implode," he said.

Intelligence experts and analysts believe Beijing's biggest concern is that a collapsed North Korea could lead to a unified and US-allied Korea on China's border and a mass migration of refugees across the Yalu river.