The CIA is investigating whether North Korea is building a new plant near the Chinese border to make nuclear-grade graphite, a mineral used to make nuclear reactors, The Washington Post reports.

The report comes one day after North Korean leader Kim Jong Un announced Pyongyang would take steps to end nuclear and intercontinental ballistic missile testing and close its atomic test site. Kim said he would “never use nuclear weapons unless there is a nuclear threat” or “transfer nuclear weapons or nuclear technology” to outsiders.

President Donald Trump, who is expected to sit down with Kim in late May or early June, praised the move, saying it was “very good news for North Korea and the world.” 

But the Post, citing a report by the Institute for Science and International Security, said North  Korea could be stringing the U.S. along, as Pyongyang has been seeking buyers for the graphite and even advertised its potency.

An English-language color handout distributed prior to this past January “mentions that the graphite can be used to make artificial isotopes or as a moderator,” writes author David Albright in a report titled, “North Korea may be proliferating controlled nuclear goods.”

“Both cases are code for use in nuclear reactors, implying that North Korea is actively seeking buyers who would use the graphite for nuclear purposes.”

The plant is reportedly being constructed in the northern city of Chongsu directly across from China.

• Gordon Chang: NKorea's Kim 'Unnerved' by Syrian Airstrikes
• Analysis: Questions Remain on NKorea's Nuclear Program