Many of the United States’ most influential pro-Israel and Jewish groups on Tuesday backed the Obama administration’s call for military action in Syria, putting strong momentum behind the effort to persuade reluctant lawmakers to authorize a strike against President Bashar al-Assad’s regime.

The stances mark a new phase in the debate over how to respond to Assad’s alleged use of chemical weapons against Syrian civilians, setting in motion a robust lobbying effort on Capitol Hill — powered in part by the memory of the Holocaust and how the Nazis gassed Jews.

After a period of conspicuous silence on the issue, major groups such as the American Israel Public Affairs Committee and the Conference of Presidents of Major American Jewish Organizations called for bipartisan consensus Tuesday around the use of force.

“Those who perpetuate such acts of wanton murder must know that they cannot do so with impunity,” the conference, which represents 52 national Jewish agencies, said in a statement. “Those who possess or seek weapons of mass destruction, particularly Iran and Hezbollah, must see that there is accountability.”

In its own strongly worded statement, AIPAC said that not taking action would weaken the United States and its ability to prevent the use of unconventional weapons.

“Simply put, barbarism on a mass scale must not be given a free pass,” the group said.

The statements came after days of intense discussions among activists about whether to play a role in the Syria debate. Some remain worried that a military strike is being cast as a move to protect Israel’s interests rather than an action to defend U.S. credibility.

“There is a desire to not make this about Israel,” said one pro-Israel advocate, who spoke on the condition of anonymity to discuss the politics of the situation. “When the administration argues to members of Congress that we should do this for Israel’s sake, that has caused deep discomfort in the Jewish community, regardless of where they stand. Israel didn’t ask the U.S. to do this.”

But some prominent Jewish leaders said a moral imperative, rooted in the experience of the Holocaust, demanded a strong response.

Abraham H. Foxman, national director of the Anti-Defamation League, participated in a call organized by the Conference of Presidents on Tuesday and said there was a clear consensus to step forward.

“To see innocent people being gassed invokes that special historical memory and sensitivity,” he said. “And when the president says it is in the national security interests of our country to stand up against such heinous violations of international norms, I think both things play very strongly in the psyche of the Jewish community.”

The Simon Wiesenthal Center, a leading Jewish human rights organization, explicitly invoked the Holocaust in a letter to lawmakers Tuesday, noting that U.S. and British officials did not respond when they were alerted in 1942 that the Nazis planned to use gas to kill Jews.

“This isn’t a Jewish issue; this is a humanitarian issue,” said Rabbi Marvin Hier, the center’s founder and dean.

Rabbi Julie Schonfeld, executive vice president of the Rabbinical Assembly, an international association of conservative rabbis, said she expects that many rabbis will address the Syrian massacre in their sermons on Rosh Hashanah, the Jewish New Year, which begins Wednesday evening.

“For the Jewish community to see people being gassed by their own leaders is something that is a horror to us, and to which we are pledged should never happen again,” she said.

The U.S. response carries significant implications for Israel. Many Israel supporters worry that a reluctance to punish Syria for its alleged use of chemical weapons could weaken the U.S. ability to contain Iran’s nuclear program. The expansion of Syria’s civil war also has heightened Israeli concerns about the direct impact of the conflict, analysts said.

“As the Syrian crisis has grown in scale, it’s become more important to Israel — with the Assad regime moving closer to Iran, the archenemy of Israel, and the rise of jihadi groups also bent on Syria’s destruction, which have been popping up in areas adjacent to Israel,” said Andrew Tabler, a senior fellow in the Program on Arab Politics at the Washington Institute for Near East Policy.

AIPAC is one of the strongest levers of influence on Capitol Hill, with ties to lawmakers on both sides of the aisle. In August, the American Israel Educational Foundation, AIPAC’s charitable affiliate, sponsored two trips of House members to Israel — one for 37 Democrats and the other for 26 Republicans.

On Tuesday, the group organized a conference call with top rabbinical allies to provide information about how to discuss the issue with their congregants, and sent a letter to its members asking for their help in persuading lawmakers to back Obama’s request to use force.

“We believe that Congress’ failure to grant the President this authority would be interpreted as a sign of American weakness, and cast doubt about whether America will act to carry out its commitments in the Middle East — including the President’s and Congress’ pledge to stop Iran from acquiring nuclear weapons,” AIPAC President Michael Kassen wrote.

A number of avowedly pro-Israel lawmakers, including House Majority Leader Eric Cantor (R-Va.), came out Tuesday in favor of a Syria strike. But others are still on the fence.

Rep. Jim Himes (D-Conn.) said he remains in the “deeply skeptical category.” Himes, who represents New York suburbs such as Stamford and Greenwich, said calls and e-mails from his district are running overwhelmingly against a military strike.

“There’s no question that the majority of my colleagues are very, very concerned about the impact of our decision on Israel, and that’s not a simple black-and-white issue,” he said. “What if we attack and Hezbollah launches an attack against Israel? I think there’s some complexity here. But it’s also true that plenty of pro-Israel groups have built deep relationships on the Hill, so I’m sure their points of view will be considered.”

Alice Crites contributed to this report.