Reuters reports that Trump didn’t know what New START was, but was sure it must be a bad deal:

In his first call as president with Russian leader Vladimir Putin, Donald Trump denounced a treaty that caps U.S. and Russian deployment of nuclear warheads as a bad deal for the United States, according to two U.S. officials and one former U.S. official with knowledge of the call. “New START has unquestionably made our country safer, an opinion widely shared by national security experts on both sides of the aisle.”

Daryl Kimball, the executive director of the Arms Control Association, a Washington-based advocacy group, said: “Unfortunately, Mr. Trump appears to be clueless about the value of this key nuclear risk reduction treaty and the unique dangers of nuclear weapons.”

Secretary of State Rex Tillerson said he supported the treaty during his Senate confirmation hearings.
When Russian President Vladimir Putin, during the January telephone conversation with President Donald Trump, raised the possibility of extending the 2010 New START treaty that caps U.S. and Russian deployment of nuclear warheads, President Trump declined, stating that this treaty is a bad deal for the United States.