As long as the DPRK feels threatened by the United States, it will feel obliged to move to nuclear weapons, Perry said. "The goal is giving each side the reasonable assurance that their security is not threatened," he said.
"There's no reason for the United States to even have troops" in South Korea if the DPRK would be no longer seen as a threat by South Korea, he added.
The former U.S. defense chief also said South Korea's decision on deploying the advanced U.S. anti-missile system of Terminal High Altitude Area Defense (THAAD) will not solve the problem.
In his opinion, "it just gives the South Korean people some reason to feel more comfortable that they could be defended."
Both China and Russia have voiced strong opposition to the THAAD deployment, pointing out that it exceeds South Korea's security needs, disrupts the regional strategic balance and jeopardizes the security interests of other countries in the region.
Referring to the Trump administration, Perry said the White House has kept sending "mixed signals."
U.S. Secretary of State Rex Tillerson said earlier this month that Washington is willing to talk to Pyongyang should it halt ballistic missile test launches. On Tuesday, Trump vowed to counter threats from Pyongyang with "fire and fury."
Hours after Trump's tough words, Tillerson said the developments do not suggest the United States is moving closer to a military option.
"I think we did not have an effective strategy," said Perry.
He also criticized the administrations of former Presidents George W. Bush and Barack Obama for adopting a "policy of strategic patience."
"It was believing something was going to happen without having a way of making it happen ... Hope is not a strategy," he said.
As a longtime advocate of a nuclear-free world, Perry called on the concerned parties of the Korean Peninsula issue to "find a way of dealing with the problem without military action."
In his opinion, "even a small military conflict is a danger because it's all too easy to escalate and become another Korean War."
