The United States should significantly bolster defensive and offensive military capabilities, drive up sanctions and take other tough measures against North Korea if yet another attempt at diplomacy fails to persuade Pyongyang to move toward denuclearization, US experts said Tuesday.

Joel Wit, a North Korea expert with Johns Hopkins University's US-Korea Institute, made the case in a joint article with Richard Sokolsky, a senior fellow at the Carnegie Endowment for International Peace, arguing what they call "coercive diplomacy" stands a chance of success with the North.

"It would lead with diplomatic engagement with the North backed by the threat of robust military and economic actions to protect the United States and its allies from an expanding North Korean nuclear program," the experts said in the article carried by the Politico newspaper.

In an effort to give diplomacy a shot, US President Donald Trump should send a private message directly to the North's leadership that his administration is willing to explore peaceful paths forward, they said. The purpose would be to start preliminary talks without preconditions to explore whether diplomacy has a chance, they added.

The broader objective of such "coercive diplomacy" would be to reach a deal with the North in which the communist nation denuclearizes in phases in exchange for concessions that "would, in the eyes of Pyongyang, end the US 'hostile policy' toward the North, they said.