LONDON — As Western powers build their case for possible military strikes in Syria, a still-forming coalition on Wednesday confronted a chorus of resistance at home, throwing up possible delays for what initially seemed like a rapid timetable for action.

In Britain, Washington’s staunchest military ally, the ghost of faulty intelligence used to justify the 2003 invasion of Iraq hung over Prime Minister David Cameron’s push to punish the government of President Bashar Assad after last week’s alleged chemical attack near Damascus.

Cameron’s government presented a draft resolution at the U.N. Security Council on Wednesday seeking to authorize “all necessary measures” to protect Syrian civilians, after Foreign Secretary William Hague said the world had to act even if the United Nations didn’t.

But hours later, tepid domestic support in Parliament for fast action forced Cameron’s government to back down from a planned vote Thursday that would have effectively paved the way for the immediate use of military force. Instead, the prime minister compromised with critics who thought that London was acting too hastily, promising to offer a watered-down measure Thursday that called for a second vote before strikes would be undertaken. That vote is likely to come next week, after U.N. inspectors now in Syria have submitted their report.

Opponents of military strikes, including a substantial minority of Cameron’s own Conservative Party, described multiple issues clouding a military response. There was the difficulty in assessing blame for last week’s attack, they said, as well as what they described as a still-vague mission goal. They also cited the chance that a strike could heighten violence in the region and drag allies into a more protracted operation, and lingering concerns that a blow against Assad’s government could strengthen extremist groups fighting within the Syrian opposition.

“I’ve had 100 emails [from constituents] on this matter and not one of them was in favor,” said Adam Holloway, a Conservative member of Parliament. “This idea that we want to draw a line in the sand is ridiculous. There is already a feeling that [former prime minister] Tony Blair allowed George W. Bush to drive drunk into Iraq, and that we can’t trust everything we’re being told. And frankly, I can understand that.”

Cameron does not require the backing of Parliament to join what would likely be a limited military operation confined to missile assaults on selected targets. But analysts called parliamentary backing vital to boosting support for action in Britain and beyond. As of Wednesday night, the opposition Labor Party was still demanding conclusive evidence of the Assad government’s culpability before supporting any military strikes.

Nations that have long resisted Western intervention in Syria, including Russia and Iran, were reasserting their opposition, saying the drumbeat was preempting the inspectors’ work. Any military action, they insisted, would only escalate violence in the region.

Some powers opposed to previous military operations in the Middle East, such as Germany, appeared to be lining up in favor of consequences for Syria in the event of conclusive guilt. But as the specter of intervention grew larger, nations considering taking part in a possible U.S.-led operation found themselves facing weak domestic support, and Jordan, a traditional ally, openly opposed military strikes.

Jordanian Information Minister Mohammad Momani said his government preferred a “diplomatic solution to the Syrian crisis” and declared that “Jordan will not be a launching pad for any military action against Syria.”

Mina al-Oraibi, assistant editor-in-chief of Asharq al-Awsat , a pan-Arab newspaper based in London, said that “Jordanians and Lebanese are terrified because they think: What happens next?”

“What if they try to retaliate on Jordan because it’s so close and there’s activity in Jordan supporting the opposition?” she said. “And there are many Lebanese who say: What if retaliation comes from Hezbollah and Israel and then Israel decides to bomb Lebanon?”

In Turkey, a nation potentially poised to join any U.S.-led operation, Prime Minister Recep Tayyip Erdogan — a former Assad ally and now one of his staunchest opponents — is confronting a public that has largely opposed military intervention with bordering Syria. On Wednesday, Devlet Bahceli, leader of Turkey’s opposition Nationalist Movement Party, called the push for action “war-mongering.” Without more details from the inspectors as well as U.N. backing, he told the Milliyet newspaper, any strikes would be “a violation of international law and would not be moral.”In South America, Venezuelan President Nicolas Maduro called military strikes part of a plot to occupy Syria. “From Venezuela, we join the voices of the world who reject those plans for an imperial military intervention against the Syrian people,” Maduro said via Twitter. “The United States and NATO countries have armed terrorist groups inside of Syria in preparation for an intervention and to control that Arab country.”

Some international leaders were urgently calling for restraint and a renewed push for diplomacy.

“Give peace a chance. Give diplomacy a chance,” U.N. Secretary-General Ban Ki-moon said in the Hague. “Stop acting and start talking.”

Even in Europe, where Britain and France have been leading calls for more assistance to Syrian rebels, analysts said there were signs that national leaders were moving toward military action without broad public support. That sense, however, appeared to be less true in France, the former colonial power in Syria that has been reasserting its military might.

Dominique Moisi, senior adviser at the French Institute for International Relations in Paris, said it was easier for President Francois Hollande to sell a joint operation with the United States in Syria to his public because Paris had taken a pass earlier on the Iraq war.

“There is no feeling here that ‘we are at it again’ or that ‘our government is lying to us,’ ” Moisi said. “We are in a better position to have public opinion favoring intervention in Syria.”

In Britain, public skepticism appeared significantly greater. A YouGov poll for the Sunday Times taken after the alleged chemical attack showed that 50 percent of those asked were opposed to British missiles being fired into Syria, with only 25 percent supporting such a move and 25 percent offering no opinion.

“European leaders, especially David Cameron in the U.K. and Francois Hollande in France, have spent months urging President Obama to consider a more serious response to Syria, but they have forgotten the basic rule of preparing and stating your case for public opinion at home,” said Jonathan Eyal, international director at the Royal United Services Institute, a London-based defense and security think tank.

Ahead of any votes in Parliament, there were calls for caution. In an interview with the Daily Telegraph published Wednesday, the influential archbishop of Canterbury, the Rev. Justin Welby, called for British lawmakers to avoid rash action.

“Is it possible to have a carefully calibrated response including armed force, if you are sure about the facts on the ground, that does not have unforeseeable ramifications across the whole Arab and Muslim world?” he asked.