The United States pledged today to deepen cooperation with allies South Korea and Japan on deterring the North Korean nuclear threat, working to ramp up pressure following worrying provocations. Leaders of the three countries urged the world community to vigilantly enforce new UN sanctions. President Barack Obama didn't disclose what further steps the countries might take as he met with Japanese Prime Minister Shinzo Abe and South Korean President Park Geun-hye on the sidelines of a nuclear security summit. But he said the countries had directed their teams to work together to help bring about a denuclearized Korean Peninsula. "We are united in our efforts to deter and defend against North Korean provocations," Obama said. "We recognize that our security is linked." Park, whose country has been repeatedly threatened by Pyongyang, warned that North Korea would face even stiffer sanctions and more isolation if it engaged in any further provocative acts. Speaking through a translator, she said the mere fact the three leaders were huddling to discuss North Korea carried "huge significance." As a nuclear security summit opened in Washington, the US said a strengthened nuclear security agreement among nations was finally set to take force, including new criminal penalties for smuggling nuclear material. The stricter rules for protecting materials and nuclear facilities worldwide were intended to reduce the likelihood of terrorists getting their hands on ingredients for a bomb.
Recent ratification by a critical mass of countries cleared the way for the changes to take effect in about a month. Though nuclear terrorism and the Islamic State group top this year's agenda, concerns about North Korea's nuclear weapons program are also commanding focus as the two-day summit gets under way. Those long-simmering concerns have escalated of late following the North's recent nuclear test and rocket launch. China's influence over North Korea will be front and center later in the day when Obama sits down with President Xi Jinping. The White House said that meeting was also an opportunity for Obama to press US concerns about human rights and China's assertive territorial claims in waters far off its coast.