SEOUL—After diplomatic consultations in Seoul, U.S. Secretary of State John Kerry virtually ruled out any possibility for renewed dialogue with North Korea over its nuclear program. Instead he called for strengthening U.S. military alliances in the region, and increasing international pressure to counter what he called Pyongyang’s provocative and disturbing behavior and disregard for human rights.

The U.S. Secretary of State John Kerry cited North Korea’s recent submarine-launched ballistic missile test as the latest example of North Korea’s continued pursuit of offensive and nuclear weapons in violation of United Nations Security Council resolutions.

And he described Kim Jong Un as “grotesque and grisly” for reportedly ordering the public execution of his highest-ranking defense minister Hyon Yong Chol with an anti-aircraft gun.

“Which makes his leadership one of the most egregious examples of reckless disregard for human rights and human beings anywhere on the planet," Kerry noted.

Pyongyang has grown increasingly isolated since it walked away from a 2005 deal with China, Japan, Russia, South Korea and the United States to end its nuclear program in return for economic aid and assistance.

North Korea has conducted three nuclear tests and numerous long-range missile tests, and some military analysts believe Pyongyang may already have as many as 20 nuclear warheads. In response to its third nuclear test in 2013, the United Nations imposed harsh economic sanctions on the regime.

One the main reasons for Secretary of State Kerry’s visit to Seoul and Beijing has been to focus on reducing regional tensions, but he says North Korea has rejected all diplomatic efforts, even from its key allies and trading partners China and Russia, to restart international talks to end its nuclear program

“Kim Jong Un has rebuffed the invitation of President Putin to go to Russia. They have rebuffed the overtures from the leaders of China to engage on this topic,” Kerry said, noting that the only way forward is to increase pressure against the Kim Jong Un regime.

The U.S., South Korea, and Japan alliance will continue to deploy the weapons and forces needed to counter the North Korean nuclear threat, Kerry said.

Washington is also talking to Beijing about increasing international sanctions against Pyongyang. Kerry says China has “extraordinary leverage” as North Korea’s largest supplier of economic aid and its biggest trading partner

Kerry says it is also growing more likely that a United Nations effort to refer North Korea to the International Criminal Court for human rights violations will succeed.