Sen. Bernie Sanders (I., Vt.) is hitting President Donald Trump for not directing the Pentagon to make climate change its number one priority.

In a press release Wednesday, Sanders, who took his honeymoon in the Soviet Union, said climate change is the biggest threat to military readiness.

“With President Trump as commander in chief, the Department of Defense, which previously called climate change a national security threat, now questions the science linking increasingly common extreme weather events to climate change,” Sanders said. “This is unacceptable and could severely jeopardize our military readiness.”

Sanders did not mention threats to combat readiness. Earlier this year Secretary of Defense Jim Mattis said he was “shocked” by the poor state of the U.S. military’s readiness for combat due to sequestration budget cuts when he returned to the Pentagon. The $700 billion military budget signed by Trump on Tuesday specifically increased spending for more “troops, jet fighters, ships, and other weapons needed to halt an erosion of the military’s combat readiness.”