The US and its allies were readying Thursday to begin major strikes against Houthi militants in Yemen who have been firing on shipping vessels in the Red Sea — just days after the Iran-backed rebels launched “the largest attack” to date.

The offensive could take place “within hours,” according to the UK Times political editor, Steven Swinford.

Officials have notified shipping executives that targets would include drone and missile launch sites, along with radar stations and weapons stockpiles in the coastal Yemeni city of Hodeida, and further inland in Hajjah, the Wall Street Journal reported.

Sites in the Yemeni capital, San’a, could also be targeted.

Tensions in the Red Sea have increased by the week since the Islamist extremist group began attacking and hijacking cargo ships passing through the vital Red Sea, a critical shipping corridor, following the outbreak of the Israel-Hamas war.

Their activities have ground commerce in the region to a halt and led some of the world’s largest shipping companies to cease operations in the Red Sea.

Despite repeated warnings from the US and allies that the Houthis would face “consequences” if they did not cease their attacks, the Houthis have repeatedly defied Western threats and continued their assaults.

The Houthis launched their largest and most complex attack yet on Tuesday, launching 18 drones and three missiles from sites in Yemen.

US and UK forces safely shot down weapons, leading US Secretary of State Anthony Blinken to promise more “consequences,” but failing to elaborate on when or what they may include.

“I’m not going to telegraph or preview anything that that might happen,” Blinken told reporters Wednesday. “We’ve been clear with more than 20 other countries that if it continues, as it did yesterday, there will be consequences.”

Other US leaders have echoed Blinken’s warning in recent days. White House defense spokesperson John Kirby also declined to “telegraph” US plans on Wednesday afternoon, but said, “We’re gonna do what we have to do.”

The Houthis have been preparing for the possibility of a US strike, the Journal reported, stockpiling their weapons in secure locations in populated areas — a tactic used by the similarly Iran-funded Hamas to deter attacks.

Houthi leaders promised to hit back with more force than ever before if the US-led coalition attacks them.

“Retaliation to any American strike will not only be at the level of the current operation, which included more than 24 drones and multiple missiles, but will be larger,” said Houthi leader Abdul-Malik al-Houthi.

The Red Sea attacks have ostensibly been targeted at vessels bringing supplies to aid Israel, but experts have said the Houthis’, and Iran’s, motivations are much broader than that.

“The Houthis and the Iranians are dictating the transit of maritime vessels on the high seas. This is incredible and the world seems powerless to stop it,” Bill Roggio, a fellow for the Foundation for Defense of Democracies, told The Post.

“This is all part of a greater Iranian plan to defeat the United States, to get the US to abandon the Middle East, so it could spread the Iranian Islamic revolution in Iraq and Syria, in Lebanon. To defeat Israel to defeat the Saudis,” Roggio said.

“The Houthis are playing their part.”