The administration of U.S. President Donald Trump has rejected a request from the Federation of American Scientists (FAS) to disclose the number of nuclear warheads possessed by the country, according to the Washington-based think tank.

The about-face in the Trump administration, which at one time did disclose information on the warheads, marks a policy shift as it emphasizes nuclear deterrence, FAS said.

The previous administration, under Barack Obama, released the number of U.S. nuclear warheads in 2010 and continued to respond to the think tank’s request for disclosure every year.

The move was in line with Obama’s pledge in 2009 to pursue a “world without nuclear weapons.” His administration also said it intended to urge China and other nuclear powers to release information as well and commit to reducing nuclear weapons.

According to an FAS report, the organization asked the U.S. Department of Energy in October to disclose the number of the country’s nuclear warheads as well as dismantled nuclear warheads as of late September last year.

In April, the department responded in a statement that, “It was determined that the requested information cannot be declassified at this time” following consideration by the U.S. Department of Defense. The statement did not cite reasons.

Hans Kristensen, an FAS nuclear expert, said the Pentagon’s response might have been influenced by the review in the U.S. nuclear program unveiled in February last year under the Trump administration.

In the Nuclear Posture Review, the administration pledged to develop low-yield nuclear warheads for increased deterrence, expanding the role of nuclear weapons compared to the previous review that was conducted in 2010 under Obama.

The Trump administration has responded only once to the think tank’s request for information disclosure, saying that at the time of the request it had possessed 3,822 nuclear warheads excluding those planned for dismantlement as of late September in 2017 — 196 fewer than the previous year.

The government also said it had dismantled 354 warheads in the year through late September 2017.

Kristensen said that with the United States shifting its stance on nuclear warhead disclosure, Russia and China “are now off the hook in international discussions about increasing transparency.”

He also said the U.S. policy shift could “certainly add to an international atmosphere of mistrust and suspicion” if a nuclear arms race continues to heat up. “That, in turn, will drive worst-case planning and make things more dangerous,” he added.