Defense Secretary James Mattis James Norman MattisBiden courts veterans amid fallout from Trump military controversies Trump says he wanted to take out Syria's Assad but Mattis opposed it Gary Cohn: 'I haven't made up my mind' on vote for president in November MORE reportedly pushed President Trump Donald John TrumpOmar fires back at Trump over rally remarks: 'This is my country' Pelosi: Trump hurrying to fill SCOTUS seat so he can repeal ObamaCare Trump mocks Biden appearance, mask use ahead of first debate MORE to seek congressional approval for last week's missile strikes against Syria but was overruled.

The New York Times reported Thursday that the Pentagon chief tried to rein in Trump, who wanted a swift and decisive strike against the Syrian regime accused of unleashing another chemical weapons attack on its own people.

In a closed-door White House meeting with defense officials last week, Mattis reportedly cited a need for more evidence that Syrian President Bashar Assad carried out the attack and warned of deepening an armed conflict with Russia, and urged the president to seek congressional approval from Congress before the strike.

The White House later denied the report.

“Reports that Secretary Mattis urged the President to seek congressional approval before last week’s strikes in Syria are categorically false," White House press secretary Sarah Huckabee Sanders said in a statement. "As Secretary Mattis explained to Congress in yesterday’s all-member briefs, the president appropriately ordered the strikes under his constitutional authorities.”

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Mattis reportedly characterized the strike on Friday as a "one-time shot" at Syria and "a very strong message to dissuade" further human rights abuses.

U.S. diplomats warned Russia in advance of the incoming strikes in order to avoid casualties.

Numerous lawmakers of both parties complained in the following days that the White House had infringed Congress's exclusive war powers listed in the Constitution.

Since the attack, Senate Foreign Relations Committee Chairman Bob Corker Robert (Bob) Phillips CorkerHas Congress captured Russia policy? Tennessee primary battle turns nasty for Republicans Cheney clashes with Trump MORE (R-Tenn.) called for Congress to reassert its authority and introduced a measure that would allow for military force in Syria, but focused on striking at the Islamic State in Iraq and Syria.

Democrats such as Sen. Tim Kaine Timothy (Tim) Michael KaineButtigieg stands in as Pence for Harris's debate practice Trump meets with potential Supreme Court pick Amy Coney Barrett at White House Names to watch as Trump picks Ginsburg replacement on Supreme Court MORE (Va.) have called the strikes "illegal" and "reckless."

Updated April 19 at 10:36 a.m.