And we have now the easily accessible documents that describe the context: Statement by Deputy Press Secretary Roussel on the Soviet Nuclear Test Ban Proposal,

And we have now the easily accessible documents that describe the context: Statement by Deputy Press Secretary Roussel on the Soviet Nuclear Test Ban Proposal, March 29, 1986 https://www.reaganlibrary.gov/research/speeches/32986b https://www.reaganlibrary.gov/research/speeches/32986b "In this initiative the President invited Mr. Gorbachev to send Soviet experts to the United States to examine our new CORRTEX verification system and to observe a U.S. nuclear test in mid-April at our Nevada test site. The President made it clear that if this meeting leads to an agreement on verification -- incorporating CORRTEX -- which meets our concerns, he is prepared to move forward toward ratification of these two treaties." White House Statement on the Soviet-United States Nuclear Testing Talks, December 15, 1988 https://www.reaganlibrary.gov/research/speeches/121588c https://www.reaganlibrary.gov/research/speeches/121588c "Under the terms of a U.S.-Soviet agreement negotiated in the previous round of the NTT and signed at the Moscow summit, underground nuclear explosions were conducted at the U.S. test site in Nevada in August and at the Soviet test site at Semipalatinsk in September, with observers from both sides present. The purpose of the JVE was to allow each side to demonstrate its preferred verification method for the TTBT and PNET. The results of the test were discussed during this round. We believe the experiments demonstrated the effectiveness and nonintrusive nature of CORRTEX, our preferred method of on-site measurement."