May 2 (UPI) -- The United Nations atomic agency director said Tuesday signs North Korea has not slowed down its nuclear weapons program is of grave concern to the international community.
The statement from the International Atomic Energy Agency came the same day U.S. analysts said the latest satellite images show a "resumption of activity" at the country's Punggye-ri nuclear test site.
IAEA Director General Yukiya Amano told the Preparatory Committee for the 2020 Review Conference on the Treaty on the Non-Proliferation of Nuclear Weapons that concerns are growing regarding North Korea's program.
"This is extremely worrying," Amano said during the session, when he also requested Pyongyang's cooperation. "Without direct access to relevant sites and locations, the Agency cannot confirm the operational status of North Korea's nuclear facilities. But all the indications suggest that North Korea is making progress with its nuclear program."
North Korea expelled all IAEA inspectors in 2009, six years after withdrawing from the Non-Proliferation Treaty in 2003.
The NPT became a means for countries to cooperate on nuclear disarmament in 1970, and currently includes 190 members.
The U.S. Permanent Representative to the Conference on Disarmament in Geneva, Ambassador Robert Wood, called on signatory states to focus on North Korea, Yonhap reported.
Wood said the United States' objective is not regime change, but to persuade Pyongyang to give up its nuclear weapons.
North Korea has remained active at its nuclear test site.
According to analysts Joseph S. Bermudez Jr. and Jack Liu, activities seen in images taken April 25, including the pumping out of water from a tunnel, show North Korea has not stopped preparing for what may be its sixth nuclear test.
There are personnel "visible outside the secondary portal," although an image of what appeared to be "volleyball games" as well as a "large number of people dispersed throughout the facility" was attributed to North Korea propaganda efforts, the analysts wrote.