Sen. Tim Kaine, D-Virginia, is calling out President Trump's authorization to launch a precision missile strike in Syria last week as an "illegal military act," slamming the administration for not coming to lawmakers on Capitol Hill first to seek congressional approval to carry out such a strike.

"We have a president, not a king, and the Constitution says it's Congress that gets to declare war, not the president," Kaine told "CBS This Morning" on Monday. Kaine suggested that if Mr. Trump "thinks he can do this without Congress, then he believes he can do anything without Congress."

He added, "What the president can do is defend the U.S. against imminent attack but if it's a matter of going on offense, against a sovereign nation of Syria, he's got to come to Congress. Especially since they've laid out that they've known for months about these chemical weapons attacks."

Kaine said that the president's strike was "one I'd likely support" if he had first brought it Congress, but stressed the administration's lack of clear strategy as an underlying issue.

"A military action isn't an end, it's a means to an end," Kaine said.

He questioned, "What's the strategy, why are we there, that's how you know a military action makes sense or not, but what the administration hasn't done is come and present to us and you saw the president 10 days ago say we're getting out of Syria and then last Friday night were dropping bombs on Syria, so we need to have that strategic discussion."

Kaine's comments come after French President Emmanuel Macron said on Sunday that he had "convinced" Mr. Trump to stay in Syria despite the president decreeing he would be pulling out troops in the region.

The White House, however, said in a statement that nothing has changed: "The U.S. mission has not changed -- the President has been clear that he wants U.S. forces to come home as quickly as possible. We are determined to completely crush ISIS and create the conditions that will prevent its return. In addition we expect our regional allies and partners to take greater responsibility both militarily and financially for securing the region"

"This is the month, April and May on the Armed Services Committee, we write the Defense Authorization bill for the year and there's going to be ample opportunity to pin the administration down on this," said Kaine on the present course in Syria.