ABC's LUIS MARTINEZ: Hagel said that U.S. inaction could emboldened to carry out even larger-scale chemical attacks which could cause even more civilian casualties. “Chemical weapons make no distinction between combatants and innocent civilians, and inflict the worst kind of indiscriminate suffering, as we have recently seen, “ said Hagel. He said inaction would undermine the credibility of America’s other security commitments, namely preventing Iran from acquiring a nuclear weapon. “The word of the United States must mean something, said Hagel. “ It is vital currency in foreign relations and international and allied commitments. ”
Sen. Barbara Boxer, D-Calif. calls for action: "I believe we cannot close our eyes to this clear violation of long-standing international norms." She says that nothing short of America's "morality" and "credibility" are on the line. However, she noted that she will not issue President Obama a "blank check."
ABC's DANA HUGHES: Despite the fact that Russia has blocked three different UN Security Council resolutions on Syria since the conflict began, and has repeatedly said it doesn’t believe the evidence the United States is presenting, Sec. Kerry offered a defense of the Washington relationship with the Kremlin.
“It’s important not to get into unnecessary struggle with the Russians over this” said Kerry who said that he thinks the Russians “are serious” about finding a political solution. Kerry said it’s important to remember Russia cooperates with us on Iran and the START treaty and other “major issues”
While today's hearing is taking place on the Senate side of the U.S. Capitol, ABC's JOHN PARKINSON reports that President Obama has collected one more supporter for military action against Syria in the House: Democratic Whip Steny Hoyer, D-Md.
“I support the President’s call for authorizing limited but decisive military action in response to the Assad regime’s use of chemical weapons in Syria. While recognizing that the details of the authorization language have yet to be finalized, the use of chemical weapons, including against innocent children, is intolerable and cannot go unanswered.," Hoyer said in a statement Tuesday afternoon.
ABC's ARLETTE SAENZ: Another protester interrupted today’s hearing. The man yelled that the U.S. has a “shameful record” of dishonesty to the American people. “Where is the moral high ground?” he said as he was escorted out of the room.
As the hearing continues, The American Israel Public Affairs Committee, the powerhouse pro-Israel lobbying group, released a statement supporting a military strike. Here's an excerpt:
"AIPAC urges Congress to grant the President the authority he has requested to protect America’s national security interests and dissuade the Syrian regime's further use of unconventional weapons. The civilized world cannot tolerate the use of these barbaric weapons, particularly against an innocent civilian population including hundreds of children. Simply put, barbarism on a mass scale must not be given a free pass. This is a critical moment when America must also send a forceful message of resolve to Iran and Hezbollah -- both of whom have provided direct and extensive military support to Assad. "
ABC's ARLETTE SAENZ: In our first look at the 2016 dynamics of this hearing, Sen. Marco Rubio, R-Fla., said that he’s a “bit skeptical” about the effectiveness of limited strikes. But Rubio also said the U.S. should have been more active to begin with. “When America ignores these problems, these problems don’t ignore us,” he said. This vote on Syria will be tough for Rubio who is already facing heat about his immigration stance from the Tea Party base that catapulted him to the Senate.
MORE FROM OUR POLL: Opposition to unilateral U.S. air strikes is essentially the same among Democrats and Republicans, at 54 and 55 percent, respectively, according to a new ABC News/Washington Post poll. It rises to 66 percent among political independents. It’s essentially identical, as well, among ideological groups, ranging from 58 to 62 percent among conservatives, moderates and liberals alike. Large majorities across these groups also oppose arming the Syrian rebels, peaking, at 78 percent, among very conservatives.
A candid acknowledgement from Sec. Kerry when asked what President Obama will do if Congress does not vote to grant authorization for a military strike against Syria: "I can't tell you what the president's going to do because he hasn't told me," Kerry told the senators.
ABC News Political Director RICK KLEIN offers his impressions of today's action on Capitol Hill so far: "Watching today’s hearing, it’s not just that President Obama has put his own credibility on the line. He’s put the nation’s credibility on the line by choosing to go to Congress. Secretary Kerry predicted celebrations in Teheran and Pyongyang if Congress turns back his request for explicit authority for military force against Syria. No wonder he can’t contemplate the what-ifs of failure – that’s a stunning thing for the secretary of state to predict, out of an action that would never have happened without the president’s decision."
Sen. John McCain, R-Ariz., referred to Sec. Kerry's wife, Teresa, who is sitting in the front row at the hearing.

ABC's DEVIN DWYER: Iran has increasingly become one of the Obama administration’s top talking points as officials make the case for military action against Syria. But in his Rose Garden remarks on Saturday, President Obama did not mention Iran a single time in announcing his decision to take military action -- and seek congressional approval.
Today, however, Secretary of State John Kerry mentioned Iran four times in his brief opening statement to the Senate Foreign Relations Committee, repeatedly tying U.S. action in Syria to deterrence of Iran’s nuclear threat. “Iran is hoping you look the other way,” Kerry bluntly told members of the committee. “Our inaction would surely give them a permission slip for them to at least misinterpret our intention if not to put it to the test. “
Defense Secretary Chuck Hagel also invoked Iran. “Our refusal to act would undermine the credibility of America's other security commitments, including the president's commitment to prevent Iran from acquiring a nuclear weapon,” he said.
Several members of the committee on both sides of the aisle appeared to share the administration’s recognition that inaction in Syria would embolden Iran. “Iran will view us as a paper tiger” if we don’t act, warned Sen. Barbara Boxer (D-Calif.).
Doing nothing “would guarantee … an emboldened Iran,” said Sen. Marco Rubio (R-Fla.) “It will also send a message to the world that there is no red line that they should fear crossing. So Iran will move forward toward nuclear weapons.”
Sen. Rand Paul, R-Ky., says in his remarks that he was "proud" of President Obama for coming to Congress for authorization of a resolution on Syria. But, Paul, added "it does concern me" that members of his administration have said (including Sec. Kerry today) that the president still has the Constitutional authority to take action without Congress' approval.
GETTING TESTY: In a testy exchange, Sen. Rand Paul, R-Ky., urged Secretary John Kerry to pledge that the president will adhere to Congress’ final decision on whether military force should be used in Syria. "Make me proud today, Secretary Kerry. If we vote you down, which is unlikely by the way, say you would go with what the people say through the. Congress and you wouldn't go forward with a war your congress doesn't support,” Paul said
“I don’t know what the president’s decision is, but I’ll tell you this, it ought to make you proud because he still has the constitutional authority,” Kerry responded.
“I don’t think he has the constitutional authority, I think the Congress has it,” Paul said asking Kerry to commit an answer.
(Kerry later turned the tables on Paul, asking him whether he thought Assad would use chemical weapons again if the United States doesn't act. Paul said it was unclear. “It’s a guarantee Assad will do it again,” if the U.S. decides not to act, Kerry said).
HILLARY CLINTON WEIGHS IN: An aide to former Secretary of State Hillary Clinton tells ABC's DANA HUGHES that “Secretary Clinton supports the President's effort to enlist the Congress in pursuing a strong and targeted response to the Assad regime's horrific use of chemical weapons.”
ABC's ARLETTE SAENZ: More than three hours into the hearing, Secretary Kerry offered a forceful defense of what a decision to not act in Syria would mean for the United States’ standing in the world, warning that this could be one of those “moments where someone didn’t stand up and act.”
“It’s not a question of what will happen if we don't do it; it's a certainty. Are you going to be comfortable if Assad, as a result of the United States not doing anything, then gasses his people yet again and they -- and the world says, why didn't the United States act? History is full of…moments where someone didn't stand up and act when it made a difference. And whether you go back to World War II or you look at a ship that was turned away from the coast of Florida and everybody on it lost their lives subsequently to German gas, those are the things that make a difference. And that's what's at stake here,” Kerry said.
An observation from ABC News correspondent JEFF ZELENY:
After nearly four hours, today's hearing has ended. Sen. Menendez predicted that the members could take up a Syria resolution as early as tomorrow.
A dispatch from ABC's JEFF ZELENY outside the hearing room: "Senator Rand Paul just told me that he has not ruled out filibustering the Syria resolution next week. In either case, he said 60 votes would be needed for passage of the resolution -- a higher hurdle than a simple majority."