Nuclear weapons

FILE - In this June 28, 2019, file photo, President Donald Trump and Russian President Vladimir Putin walk to participate in a group photo at the G20 summit in Osaka, Japan. The Trump administration is notifying international partners that it is pulling out of a treaty that permits 30-plus nations to conduct unarmed, observation flights over each other’s territory — overflights set up decades ago to promote trust and avert conflict. The administration says it wants out of the Open Skies Treaty because Russia is violating the pact and imagery collected during the flights can be obtained quickly at less cost from U.S. or commercial satellites. (AP Photo/Susan Walsh, File)

Russian President Vladimir Putin attends a meeting on the transport system development via video conference at the Novo-Ogaryovo residence outside Moscow, Russia, Thursday, May 7, 2020. (Alexei Nikolsky, Sputnik, Kremlin Pool Photo via AP)

In this photo released Wednesday, April 22, 2020, by Sepahnews, an Iranian rocket carrying a satellite is launched from an undisclosed site believed to be in Iran's Semnan province. Iran's Revolutionary Guard said Wednesday it put the Islamic Republic's first military satellite into orbit, dramatically unveiling what experts described as a secret space program with a surprise launch that came amid wider tensions with the United States. (Sepahnews via AP)

FILE - In this file photo taken from undated footage distributed by Russian Defense Ministry Press Service, an intercontinental ballistic missile Avangard lifts off from a truck-mounted launcher somewhere in Russia. Russian Deputy Foreign Minister Sergei Ryabkov said the Avangard can be included in the New START arms reduction treaty with the United States. (Russian Defense Ministry Press Service via AP, File)

Medical staff members arrive for a duty shift at Dongsan Hospital in Daegu, South Korea, Friday, March 27, 2020. The new coronavirus causes mild or moderate symptoms for most people, but for some, especially older adults and people with existing health problems, it can cause more severe illness or death.(Lee Yong-hwan/Newsis via AP)

Colorado National Guard medical personnel prepare to perform coronavirus test on a motorist at a drive-thru testing site outside the Denver Coliseum Saturday, March 14, 2020, in Denver. Officials planned to administer 150 tests but the line of vehicles wrapped around three city blocks. For most people, the new coronavirus causes only mild or moderate symptoms. For some it can cause more severe illness. (AP Photo/David Zalubowski)

Director General of International Atomic Energy Agency, IAEA, Rafael Mariano Grossi from Argentina, talks prior to the start of the IAEA board of governors meeting at the International Center in Vienna, Austria, Monday, March 9, 2020. (AP Photo/Ronald Zak)

FILE - In this Jan. 8, 2020, file photo, Defense Secretary Mark Esper arrives to brief members of the Senate on the details of the threat that prompted the U.S. to kill Iranian Gen. Qassem Soleimani in Iraq on Capitol Hill in Washington. When President Donald Trump laments the “craziness” of spending billions of dollars to modernize America's nuclear weapons, he is referring in part to plans for replacing the B-52 bombers and silo-based missiles that stand ready near Minot, N.D. Esper visited Minot on Wednesday, Feb. 19, for a firsthand look. (AP Photo/ Jacquelyn Martin, File)