Rand Paul believes the Islamic State has “absolutely” declared war on the U.S., and he think the U.S. must “destroy” the extremist group. The Kentucky Republican senator told Fox News Wednesday that President Obama’s failure to bring the case for war to Congress “weakens America.”

“Intervention isn’t always the answer,” Paul told Fox News’ Sean Hannity. He said that in certain cases, like the situation in Libya, foreign intervention actually has allowed for extremist groups to flourish.

In Syria, Paul said, the Islamic State -- formerly known as the Islamic State of Iraq and Syria (ISIS) -- rose to power rapidly because the Obama administration previously (and currently) funded rebel groups in Syria.

Last week Paul made a similar criticism of Hillary Clinton in an op-ed piece published in the Wall Street Journal. He argued that if Clinton and her “war hawk” ways would have been gotten the job done, a regime change in Syria might have led to ISIS claiming the presidency.

Still, Paul’s solution is to call a joint Congress session immediately and make the case for war in Syria. According to the U.S. constitution, only Congress is allowed to initiate a war.

Earlier on Wednesday Paul told the Associated Press, "If I were president, I would call a joint session of Congress. I would lay out the reasoning of why ISIS is a threat to our national security and seek congressional authorization to destroy ISIS militarily."

Paul joined the ranks of Sen. Lindsey Graham (R-S.C.) and Sen. Bill Nelson (D-Fla.), who called for immediate action against the Islamic State in Syria. On Tuesday, Nelson announced he would introduce legislation next week that would allow Obama to bomb ISIS in Syria without permission from Congress.

Last week, Obama said the U.S. had no strategy to tackle ISIS in Syria yet -- a point his press secretary quickly rushed to clarify. But Obama did say he intended to bring the Syria situation to Congress, which would mean bringing the case for war, and not with just air strikes like those taking place in Iraq.

“We're going to cobble together the kind of coalition that we need for a long-term strategy as soon as we are able to fit together the military, political and economic components of that strategy," Obama said last week.

The need to defeat ISIS became an even more urgent matter to Congress and the Obama administration after the militants released a video of U.S. journalist Steven Sotloff's beheading -- the second video of its kind in two weeks.

“We’re not going to let our enemies behead our journalists,” Paul said.