Several members of the Massachusetts Congressional delegation called for caution and forethought in the nation’s approach to Syria, which might include military force.

U.S. Sens. Elizabeth Warren, Ed Markey, and Congressmen John Tierney, Michael Capuano and Stephen Lynch indicated openness to the use of force, while calling for more information and in some cases the assertion of Congress’s constitutional power to declare war.

“The one thing that I’m absolutely certain of is that Congress has to be consulted and in my opinion, consulted means more than just informed. In my opinion it means Congress has to be asked for permission to use military force,” Capuano said.

Secretary of State John Kerry has said Syria’s “indiscriminate slaughter of civilians” with chemical weapons is “undeniable” and “defies any code of morality.”

Syrian President Bashar al-Assad has been at war with rebels within the country since “Arab spring” protests in 2011 were met with a violent governmental crackdown. Last week, reports emerged that a rebel-held suburb of the capital, Damascus, had been attacked with a chemical weapon, killing hundreds of people, some of whom had hunkered in their basements for cover from the shelling.

Warren echoed Kerry’s indignation, while urging caution as the United States weighs its options.

“There is no doubt that what Assad – or I think there is not doubt at this point – that what Assad has done violates international law. This is a violation against all the people of the world, not just the people of the United States, but all the people,” Warren said Wednesday, when asked if Syria posed a direct threat. She said, “At this point, it’s about identifying that we have a goal, and that we have a reasonable way to get there. But I want to caution on this. It’s critically important that we remember about unintended consequences. We may have good intentions, but the consequences of our acts are not limited by those intentions.”

Tierney, who voted against the Iraq War authorization and questioned the lack of support for a strike in the region, said President Barack Obama should call Congress back into session, and lay out the evidence.

“Where’s the Arab League on this whole thing, and why aren’t they standing up? . . . I think Turkey is supportive of somebody else doing something that they ought to be stepping forward and taking a lead on,” Tierney said. “The United States doesn’t always have to be the most outraged and the most aggressive.”

Obama did not seek Congressional approval for a series of missile attacks and air raids over Libya, which helped the rebel fighters there depose and eventually kill the country’s leader Moammar Gaddafi.

Capuano, who joined other lawmakers in a lawsuit against the commander in chief for failing to consult Congress about the Libyan intervention, said he would be open to the argument of military involvement if he is satisfied the Assad government used chemical weapons.

“If it’s proven, I would listen to it. But the use of military force is not a short-term thing. It also opens up the issues of what happens to the rest of the region, what happens after the use of military force,” Capuano told reporters.

Lynch and Markey both saw routes for a military engagement, with restrictions.

“I do believe that the opportunity to use NATO might be available. I certainly don’t think the United States should go in there without considerable international support and probably with full NATO support,” Lynch said. He said, “I would not support the U.S. going in there unilaterally.”

“It is important for the United States to stand up and say, ‘No, chemical weapons cannot be used.’ At the same time, we do not want to involve ourselves with ground troops in a civil war in Syria,” said Markey. He said, “Congress should exercise its prerogative” on use of the military, and said, “I would hear the case that was made.”