American intelligence agencies received what is considered conclusive evidence that Russia provided hacked material the Democratic National Committee to WikiLeaks after the November elections, according to three U.S. officials.

Intelligence agencies concluded before the election that Russia directed the hacking but lacked conclusive evidence that it provided the material to WikiLeaks in an attempt to damage Democratic presidential nominee Hillary Clinton, Reuters reported.

The new information supposedly provided impetus for President Barack Obama’s decision to expel 35 suspected Russian spies and sanction two spy agencies.

Obama had supposedly told Russian President Vladimir Putin to “knock it off,” but refrained from taking action as it might have been seen as an effort to assist Clinton and discredit Republican rival Donald Trump.

[Graham Blasts Trump Over Taking Assange’s Side]

The Senate Armed Services Committee will hold a briefing on the Obama Administration’s response on Thursday. Committee Chairman Sen. John McCain, R-Ariz., has called Russian interference “an act of war.”

The revelations come as Trump has expressed doubts about Russian interference and praised WikiLeaks editor Julian Assange.