WASHINGTON — The United States needs to contain an increasingly assertive North Korea and look to China along with other countries in the Asia-Pacific region for support in negotiations with the unpredictable communist country, former Secretary of Defense William Perry said Monday.

North Korea’s most recent test was designed to determine how to make nuclear weapons compact enough to “fit into the warhead of a nuclear missile”, according to Perry who served under the Clinton administration.

Perry spoke along with three other former defense secretaries, William Cohen, Harold Brown and Chuck Hagel, in a “Leaders Speak” panel hosted by the National Committee of the United States China Relations. The previous officeholders advised incumbent Secretary of Defense Ash Carter and the Obama administration to rally with China in order to eliminate the North Korean threat.

Perry said that when he held office, North Korea agreed to freeze its activities beyond their nuclear facility and complied. However, that agreed framework was “terminated early” and “it was a mistake to give that up and make that history.”

“The best basis I can think of for negotiating strategy [with North Korea] is no new nuclear weapons, no creating more nuclear weapons, no transfer of nuclear weapons,” Perry said.

Although it wouldn’t be the same as asking North Korea to completely eliminate its arsenal, Perry viewed this as a good base containment strategy. The U.S. could work with from China — who supplies North Korea with food and fuel — and other countries to go forward in talks with North Korea, he said.

Brown questioned the “quid pro quo” for agreeing to such guidelines, or what the North Koreans would be getting out of such an agreement.

Cohen suggested a multilateral and unilateral push to “squeeze the North Korean elite” and “reimpose previous sanctions”.

“What do they get out of this? What have they been getting out of this? They will have been engaged in extortion,” Cohen said. “We’ll inspect shipments coming out of North Korea that are suspect and going to various ports, and we should insist that our [Chinese] allies open those cargoes for inspection, and not make it mandatory, not optional.”

Hagel added that it was clearly in China’s self interest to be on board as “the last thing they need is millions of Koreans fleeing across their border.”