The Obama administration is already planning "for every contingency" in case of any fallout from US military strikes against the Syrian regime, a top White House official said Sunday.
But Chief of Staff Denis McDonough refused to be drawn on whether President Barack Obama would go ahead with any strikes if Congress refuses to give military action a green light, nor would he be drawn on any specifics.
"The risks are many fold. One, the risk that somehow we get dragged into the middle of an ongoing civil war," McDonough said on CNN's State of the Union as Obama prepares to address the nation on Tuesday about the Syria crisis.
"We have to obviously be very careful and very targeted and very limited in our engagement so we do not get dragged into the middle of this. And then there's obviously risk of reaction and retaliation against our friends," McDonough acknowledged.
"We are obviously providing for it and planning for every contingency in that regard and we'll be ready for that."
The Obama administration has for the past couple of weeks sought to shore up support both at home and abroad for limited military strikes against Syria in retaliation for what it says is the regime's use of chemical weapons in a Damascus suburb.
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After days of classified and open hearings last week, the full Congress is due to debate Obama's call for military strikes when it returns from its summer break on Monday. However there remains deep skepticism about involving the United States in another war abroad.
A congressional panel Saturday released graphic videos of what it said was the August 21 attack, showing men and children writhing in pain, apparently foaming at the mouth and vomiting.
"I hope every member of Congress before he or she decides how to cast a vote will look at the videos. It's unbelievably horrendous," McDonough told Fox News Sunday, blaming the regime of Syrian President Bashar al-Assad for unleashing chemical arms.
He said more than 400 children were believed "killed by this heinous attack using this weapon which has been prohibited in much of the rest of the world for a hundred years."
US Secretary of State John Kerry was meeting Arab League leaders in Paris on Sunday on a diplomatic offensive to win more international support for US military strikes, after G20 nations emerged split from a summit in Russia with only just over half calling for a "strong response" to the chemical weapons attack.
"We do have plenty of friends who are standing with us. Let's remember where the president said it's an international red line. Going back almost 100 years, 1925, the Geneva protocol," McDonough said on CNN.
But he admitted that so far he didn't believe there was specific military support offered by other countries.
"Not at this point but it is specific support for holding him to account and it is a recognition that it happened. We are no longer debating whether it happened or whether it didn't happen. That's important."