Members of the Bay State’s congressional delegation gave a cool reception yesterday to the Obama ?administration’s initial plans to strike Syria, with some framing the proposal as too “open-ended” and at least one saying he can’t support it as it stands — underscoring the uphill battle the president faces in launching an international attack.

“There’s a lot more questions that have to be answered before I’m ready to support military action. Right now, I’m not,” said U.S. Rep. Michael Capuano, who said that while he’s all but convinced Syrian President Bashar Assad is behind an Aug. 21 chemical weapons attack, the “most important question is what happens after” a U.S.-led strike.

“For me, it’s not about whether he’s a bad guy, it’s not about whether he committed a war crime. It’s about whether we can make the situation better or make it worse,” said the Somerville Democrat, usually one of Obama’s steadiest backers on the Hill.

Secretary of State John F. Kerry and other administration officials are slated to testify in multiple hearings today on Capitol Hill, where members of Congress were briefed yesterday and will be again today.

Obama’s decision to seek a congressional green light before military action has drawn support and criticism on both sides of the aisle, with some — like Arizona U.S. Sen. John McCain — pushing for actions that go beyond the president’s plan of a limited strike.

Like McCain, Bay State U.S. Sens. Elizabeth Warren and Edward J. Markey — both ordinarily staunch supporters of the president — said they needed more details, and declined to publicly back or denounce a strike.

“I think if you read the proposal, it’s clear that it’s very open-ended, and I think that’s a problem,” Warren said. “We understand from our earlier experiences (including in Iraq) that we might have limited objectives at the beginning, but there can be many unintended consequences … that unfold over time.”

Markey said administration officials on Sunday laid out some but not all of the classified evidence they have on the attack that left nearly 1,500 dead, and said he intends to see more.

“We have to be very ?sober in a decision of this nature,” said Markey, who last week said he wouldn’t support putting troops on the ground, but mentioned missile strikes as one ?avenue Obama could explore. He emphasized yesterday that he hasn’t decided?how he would vote.

“We need a debate in Congress,” he said.

And the debate should not be hasty, he and other legislators said.

“I do think Congress is going to take a little more time than most people might want,” Capuano said. “Democracy is sometimes messy. Having one person make a decision is obviously quicker and easier, but it’s not the way we should get involved with war.”