Sen. Bob Menendez, the top Democrat on the Senate Foreign Relations Committee, cautioned the Trump administration that "it's not time to put a 'Mission Accomplished' banner over the White House," just days after the covert U.S. military operation in Syria that resulted in the death of Islamic State leader Abu Bakr al-Baghdadi.

"The end of Bin Laden was not the end of Al Qaeda and the end of al-Baghdadi is not the end of ISIS," the New Jersey senator said, noting that U.S. officials have estimated that thousands of ISIS terrorists remained in Syria. "ISIS is still a challenge to the national interests and security of the United States... the Kurds have to defend themselves at the end of the day, versus worrying about detaining ISIS prisoners."

He continued, "You have a reconstituted force of nearly 30,000 ISIS fighters. That is a clear and present danger to the national security of the United States."

President Trump confirmed the terror leader's death at a news conference Sunday as congressional Democrats decried that they were left in the dark about the covert mission that had been planned for months and involved significant intelligence from Kurdish allies in Syria – including a rare informant at the heart of ISIS who was in the compound at the time of the raid.

He also said he declined to inform Democrats ahead of time because he wanted the raid "kept secret" until after it happened.

Many Democrats also said they were skeptical the administration had a clear-cut plan to eradicate the terrorist organization.

"We have been asking for and cannot get -- what is the definitive strategy to defeat ISIS by this administration?" Menendez asked.

ISIS LEADER BAGHDADI'S UNDERWEAR STOLEN BY KURDISH SPY FOR DNA TEST BEFORE RAID, OFFICIAL SAYS

A Senate official confirmed to Fox News on Monday that ranking members of the intelligence community, including Defense Secretary Mark Esper and Gen. Mark Milley, the chairman of the Joint Chiefs of Staff, would brief senators Wednesday about the successful raid that resulted in Baghdadi detonating a suicide vest that killed him and three of his children.

The military operation took place weeks after the president ordered the withdrawal of nearly 1,000 armed forces from northern Syria.

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Senate Minority Leader Chuck Schumer, D-N.Y., also said Tuesday that Congress has "not heard a single word from the Trump administration about what to do about the escaped prisoners," referring to at least 100 ISIS prisoners whom the Kurds held captive but who later escaped in Syria following Turkey’s invasion of the region.

Fox News' Benjamin Hall contributed to this report.