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."

"The Department of Defense should be doing all it can to fight the causes and prepare for the impacts of climate change to prevent threats to our national security, not questioning virtually the entire scientific community," Sanders said.

The Vermont senator has claimed climate change is the greatest threat to national security before.

Sanders returned to the subject again after the recent release of a Government Accountability Office report that revealed the Pentagon does not track the costs of weather effects on overseas installations because "there is no requirement" to do so.

Sanders's office said the report shows the Pentagon's "rejection of established climate science."

"After reviewing mounting evidence from the Government Accountability Office that climate change has reduced military readiness, President Donald Trump's administration rejected the science attributing extreme weather events to climate change as well as recommendations to monitor the effects of climate change," Sanders's office said.

The Vermont socialist and former Democratic candidate for president also criticized Trump's Department of Defense for partially disagreeing with the GAO's recommendations.

The Pentagon "noted that currently, associating a single event to climate change is difficult and does not warrant the time and money expended in doing so."