U.S. Senator Edward Markey (D-MA) alongside Senate Democrats speaks during a press conference addressing a new policy that demands recipients of foreign military aid to follow international humanitarian law at the U.S. Capitol in Washington, U.S., February 9, 2024. REUTERS/Nathan Howard

By Timothy Gardner

WASHINGTON (Reuters) -Democratic U.S. Senator Edward Markey on Tuesday urged President Donald Trump not to resume explosive nuclear weapons testing, saying doing so could spur rival nuclear powers Russia and China to do the same.

Trump late last month announced on social media he was directing the Pentagon to immediately restart the process for testing nuclear weapons after a halt of 33 years. His move caused confusion as the National Nuclear Security Administration, a branch of the Energy Department, is the agency that would carry out explosive nuclear weapons tests.

"Even one small U.S. nuclear test would give Russia and China the green light to conduct many large nuclear tests that would be much more useful for the development of new nuclear weapons that could pose a threat to U.S. national security," Markey, a co-chair of the Nuclear Weapons and Arms Control Working Group that has members in both the Senate and in the House of Representatives, wrote in a letter to Trump.

Markey, a longtime leader of non-proliferation efforts in Congress, also pushed Trump during his first presidential term in 2020 against resuming explosive nuclear weapons tests.

Trump has said the U.S. would carry out the tests "like other countries do." CIA Director John Ratcliffe said on social media on November 3 that Trump "is right" about other countries testing nuclear weapons.

In response to Trump, Russian President Vladimir Putin ordered his top officials to draft proposals for a possible test of nuclear weapons, something Moscow has not done since the 1991 collapse of the Soviet Union.

Trump has suggested that Russia and China are conducting small nuclear tests that are hard to detect, known as hydronuclear tests, in violation of U.S. policy and the Comprehensive Test Ban Treaty, Markey said in the letter.

"Reports of such tests from 2019 raise concerns, but they are unconfirmed," Markey said. "Even if true, they would not justify renewed U.S. nuclear testing."

Markey asked Trump for evidence by December 15 that Russia and China are conducting secret nuclear tests. He also asked Trump whether his statements reflect a misunderstanding of the difference between missile tests and nuclear explosive tests.

The White House did not immediately respond to a request for comment.

(Reporting by Timothy Gardner, editing by Deepa Babington)