National Security Adviser Susan Rice laid out the case today for action in Syria, saying that the Assad regime's use of chemical weapons poses a threat to America's national security

"Every time chemical weapons are moved, unloaded and used on the battlefield, it raises the likelihood that these weapons will fall into the hands of terrorists active in Syria, including Assad's ally, Hezbollah, and al-Qaida affiliates," she said at a Washington think tank.

"That prospect puts Americans at risk of chemical attacks targeted at our soldiers and diplomats in the region and even potentially our citizens at home.

Rice said the United States did not believe this could escalate into a bigger war, but given the risk, the administration is still taking a range of measures to safeguard U.S. allies and personnel. She did not detail what those measures are, but did have a warning for President Assad and allies, saying that they would be " more than foolish" to strike back at the U.S.

"They know that President Obama throughout his presidency has amply demonstrated he will not hesitate to defend our nation, our citizens and our allies against direct threats to our security."

Speaking at the New American Foundation in Washington for more than 40 minutes, Rice said that failing to respond to Assad would make future chemical weapons attacks more likely from Syria, as well as ensuring that more of the country's civilians will "die from Assad's poisonous stockpiles."

She again brought the issue back to America, saying that the U.S. remains vulnerable since Assad is so closely allied with Iran and terrorists groups such as Hezbollah.

"Failing to respond brings us closer to the day when terrorists might gain and use chemical weapons against Americans abroad and at home," Rice told the audience at the think tank.

Rice also said that if Congress does not authorize military action, the message sent to not only U.S. foes but to its allies will be one of weakness, raising questions around the world about America's ability to protect its national interests . The former United Nations ambassador said a congressional no vote will make it harder to for the U.S. to build coalitions in the future.

She touched on her time at the U.N. serving during President Obama's first term and echoed the sentiments of current U.N. Ambassador Samantha Power, saying that diplomacy alone in Syria is no longer a viable option. She pointed out that Russia and China have double vetoed "almost meaningless resolutions" three times since the conflict has began.

"Let's be realistic, it's just not going to happen now," said Rice. "Believe me, I know. I was there for all of those U.N. debates and negotiations on Syria. I lived it, and it was shameful."

Rice also reiterated the administration's argument on the nature of the strikes, saying that they will be limited in scope. She said that any military operation would not be like Iraq or Afghanistan, but it also wouldn't be like Kosovo or Libya either, which both featured sustained air campaigns.

She compared the action to when President Reagan hit Libya in 1986, and President Clinton launched limited missile strikes in Iraq in 1998. Rice argued that those situations "are proof that the United States is fully capable of conducting limited, defined and proportional military actions without getting enmeshed in a drawn-out conflict."

Rice also said a military strike would show Syria that the United States could strike again if the regime continues to use chemical weapons.

"If Assad is so brazen as to use chemical weapons again, he would know that we possess the ability to further degrade his capabilities," she said.

She ended her nearly hour-long remarks with an emotional appeal. Rice pointed out that she has been to many war zones in her long career, but as a mother of two children, she said she finds the images of the chemical weapons attack in Syria particularly "gut wrenching."

"Children lined up in shrouds, their voices forever silenced; devastated mothers and fathers kissing their children goodbye, some pulling the white sheet up tight around their beautiful faces as if tucking them in for the last time," she said.

Rice called on Congress and the American public to watch the videos for themselves, "see that suffering, look at the eyes of those men and women, those babies, and dare to turn away and forsake them," she implored. "Imagine the months and years ahead where an emboldened Assad and those who follow his example carry out more attacks, forcing us to witness more and more such depravity."

"There are no words of condemnation strong enough to capture such infinite cruelty," she said. "But where words may fail us action must not."