Washington (CNN) - Making a case for military action in Syria, Secretary of State John Kerry and other top administration officials told House Democrats in a phone call Monday to expect more international support in the coming days and argued the collateral damage of any strike would be low, according to two sources on the call.
While both sources said the tone among House Democrats was more positive than expected–given their anti-war fervor over the years–one source said there was still a "healthy dose of skepticism and concern."
The latest call illustrates the lack of clarity over which way the House will vote when it reconvenes next week after recess.
"Anybody who tells you with any degree of confidence that they know where this is going to end up, should not be in the business of predicting," a Democratic member told CNN after the conference call.
The call came as the White House attempts to generate support from unconvinced lawmakers for the president's proposal to take military action in Syria. In a surprise announcement, Obama said Saturday he would seek congressional authorization first, though he maintained he still has a right to take unilateral action.
About 70 lawmakers came back from recess on Sunday for a classified briefing with administration officials, and more briefings and hearings will take place throughout the week.
Sources said Rep. Rick Nolan, D-Minnesota, was perhaps the most vocal on Monday's phone call. He argued the Obama administration is suffering from "historical amnesia" and forgetting lessons from the wars in Vietnam and Iraq.
Kerry responded forcefully, saying Syria is different and that as a former prosecutor, he believes this is the right thing to do beyond a reasonable doubt, according to the sources on the call.
Kerry labeled the situation with Syria as a "Munich moment," referring to the 1938 Munich Agreement between Nazi Germany, France, Great Britain, and Italy that allowed Germany to take part of Czechoslovakia in order to prevent all-out war in Europe at the time.
Other skeptics wanted to know more about collateral damage, a source said.
Along with Kerry, Chairman of the Joint Chiefs of Staff Martin Dempsey, Defense Secretary Chuck Hagel, and National Security Adviser Susan Rice were on the 70-minute call, while 127 Democratic members dialed in, according to a Democratic aide.
While the British Parliament voted down a measure to join an international coalition last week, Kerry said Turkey, Saudi Arabia and the United Arab Emirates have offered to use military assets for any action planned for Syria, sources said. As the week goes on, he continued, more countries will grow favorable towards taking action.
Dempsey argued they estimate collateral damage in a military attack would be low, sources said. But later there was a discussion over what that means and how they can really know.
For her part, Rice argued the crisis in Syria is at the core of U.S. national security interests, because of the use of chemical weapons and possible proliferation.
House Democratic Leader Nancy Pelosi at one point asked Kerry if she could interrupt and made the point in support of using force, saying that punishing Bashar Al-Assad for using chemical weapons should be a pillar of national security, according to sources on the call.
Pelosi doesn't plan to whip the Syria vote, meaning top House Democrats won't overtly twist arms to get votes. But the Democratic leader is making her view known, like she did in the call, and Democratic leadership will count the anticipated votes so they know where they stand heading into the vote.
Pelosi will join House Speaker John Boehner Tuesday morning for a meeting at the White House, according to congressional aides.