President Obama's decision to send U.S. troops into Syria is reigniting the debate in Congress over long-stalled legislation authorizing the war.

The administration announced Friday that it would send approximately 50 special operations troops into Syria in an advisory role, putting U.S. boots on the ground in the country for the first time since the country's civil war began.

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Democrats pounced on the decision, suggesting that it underscores the need for Congress to take up and pass an authorization for use of force (AUMF), which could also place boundaries on military operations against the Islamic State in Iraq and Syria (ISIS).

"Regardless of my views, the War Powers Resolution requires Congress to debate and authorize the escalation of U.S. military involvement in Syria," Sen. Brian Schatz (D-Hawaii) said, calling the administration's decision to send troops into the country a "mistake."

An AUMF proposal that the administration submitted to lawmakers earlier this year sparked concerns from both parties over language banning any "enduring offensive ground combat operations." While Republicans feared the language could tie the hands of the military, Democrats worried it would be vague enough to create legal backing for an open-ended ground war.

“The bottom line is that it is well past time for Congress to do our constitutional duty and debate an authorization for the war against ISIL in Iraq and Syria," he added, using an alternative acronym for ISIS. "I hope that in the shadow of this new escalation, Congress will do its job and debate and pass an authorization to give legal standing to the administration’s fight against ISIL.”

"Well there's a lot of folks … who don't think we can pull together an authorization across the very big differences," he told MSNBC on Friday.

Kaine reiterated his position Friday, saying that "it is time for Congress to do its most solemn job, to debate and declare war."

The Virginia Democrat told The Hill earlier this month that while his colleagues on the Foreign Relations Committee increasingly acknowledged that legislation needed to be passed, there were few signs of action.

Underscoring the political differences, Republicans largely focused on the need for a strategy from Obama in the wake of Friday's announcement.

In the House, lawmakers defeated a push by Rep. Jim McGovern (D-Mass.) earlier this year that would have required removal of troops from Iraq and Syria within 30 days. The move was part of an effort by McGovern to either remove troops or force Congress to pass legislation authorizing the war.

McGovern said Friday that Americans want to know that Washington has "a clear plan to bring this conflict to a peaceful end," adding that "this starts with Congress doing its job and voting on an AUMF."