TOKYO — North Korea has threatened to restart the development of its nuclear weapons program unless the United States lifts sanctions, underscoring one of the major potential stumbling blocks in Washington’s diplomatic outreach with North Korean leader Kim Jong Un.

The Trump administration has insisted that sanctions and other pressures remain on North Korea until it dismantles its nuclear program. Kim’s regime, however, has always demanded a step-by-step process of denuclearization that would include lifting U.S. sanctions along the way.

In the past month, Pyongyang has stepped up its calls for sanctions relief. The statement released late Friday by North Korea’s Foreign Ministry is the latest indication that negotiations over its nuclear program have hit an impasse.

The issue of sanctions has also created a rift between Seoul and Washington.

South Korea has backed the North’s call for sanctions relief, and is keen to get moving on an ambitious program of economic development and cooperation, including building road and rail links across their heavily militarized frontier.

The North Korean Foreign Ministry warned that unless sanctions were lifted and Washington stopped behaving “arrogantly,” North Korea could reinstate “pyongjin” – its policy of simultaneously developing its nuclear weapons program alongside seeking economic development.

In April, Kim declared that the country’s nuclear weapons program was sufficiently advanced, and that the policy of “pyongjin” would replaced by a single focus on improving the economy. Backtracking could reignite tensions with the United States.

Still, neither side has turned its back on negotiations.

Secretary of State Mike Pompeo told journalists that he will meet his North Korean “counterpart” for further talks next week.