A senior State Department official told senators on Tuesday that the United States remains in the assessment phase on implementing President Donald Trump’s October instruction to resume nuclear weapons testing.
Undersecretary of State for Arms Control and International Security Thomas DiNanno informed the Senate Foreign Relations Committee that the U.S. has not held discussions about conducting atmospheric nuclear tests. He noted that the last atmospheric nuclear weapons test carried out by the United States occurred in 1962.
When asked whether underground explosive testing might be reconsidered, DiNanno did not rule it out. The last explosive underground test by the United States took place in 1992. On the prospect of a renewed testing program, he said:
"We’ve made no decision specifically on how or what any testing program would look like."
DiNanno’s remarks followed a question from senators on how the presidential directive to resume testing was being executed. He reiterated U.S. charges that both Russia and China have carried out explosive underground nuclear tests. The official acknowledged that Moscow and Beijing deny those charges and that some experts have challenged the U.S. assertions.
The testimony made clear that while a presidential directive exists, specific plans, formats and modalities for any future U.S. tests have not been finalized. DiNanno communicated two distinct limits so far: discussions on atmospheric testing have not taken place, and no conclusive decisions have been reached about the nature of a testing program.
This position highlights continuing uncertainty within U.S. policy circles about the operational shape of any move to resume testing and underscores ongoing disputes over whether other nuclear-armed states have themselves conducted similar underground explosive tests.
As the assessment process continues, the Senate hearing provided lawmakers with an updated official account but did not yield firm policy choices or timelines.