Only sanctions can lead to a change in North Korea's nuclear calculus, the U.S. treasury secretary said Wednesday, calling for stringent implementation of the latest package of U.N. Security Council sanctions.

Secretary Jack Lew made the remark during a discussion at the Carnegie Endowment for International Peace, saying the U.S. is working closely with China and others to carry out the new sanctions that are considered the toughest ever to be imposed on Pyongyang.

"We are mindful, though, that North Korea's leadership has prioritized the pursuit of nuclear weapons over just about anything else, including economic growth or the day-to-day lives of its own people," Lew said. 

"But it is precisely because of this that we must work closely with China and others in the region to ensure strong implementation of the new sanctions. Only with robust international cooperation can we convince Pyongyang to change its calculus and stop its activities," he said.

Lew also said that the latest U.N. sanctions underline for the North Korean regime the international community's resolve to stop its nuclear and missile programs.

The sanctions, along with unilateral measures the U.S. has imposed on Pyongyang, "will increase the pressure on North Korea in several key economic sectors, including banking, transportation, mining and metals, and labor," the secretary said.

The sanctions require mandatory inspection of all cargo going in and out of the North, regardless of whether by land, sea or air, while banning its exports of coal, iron and other mineral resources, a key source of hard currency that accounts for nearly half of the country's total exports.

It also prohibits all small arms and other conventional weapons from being sold to the North, bans jet and rocket fuel supplies to the country, grounds North Korean flights suspected of carrying contraband and denies vessels carrying illicit items access to ports. (Yonhap)