The new leader of Democrats in the Senate says Donald Trump is being "really dumb" for picking a fight with intelligence officials, suggesting they have ways to strike back, after the president-elect speculated Tuesday that his "so-called" briefing about Russian cyberattacks had been delayed in order to build a case.

"Let me tell you: You take on the intelligence community — they have six ways from Sunday at getting back at you," said Senate Minority Leader Chuck Schumer Tuesday evening on MSNBC after host Rachel Maddow informed him that intelligence sources told NBC news that the briefing had not been delayed.

"So, even for a practical supposedly hard-nosed businessman, he's being really dumb to do this," he added.

Trump has repeatedly expressed skepticism about the U.S. intelligence community's conclusion that Russia was in all likelihood involved in a hacking plot aimed at interfering in the election. He claimed over the weekend that he knew "things that other people don't know" and hinted that further information would soon be on the way. "You'll find out on Tuesday or Wednesday," he told reporters.

That information was expected to be provided to Trump mid-week via an intelligence briefing. But Tuesday evening, Trump said his briefing was delayed until Friday, and speculated that the spooks might need more time to build their case. "Very strange!" he added.