WASHINGTON: The US military chief and senior lawmakers warned on Sunday that the terror threat that caused the closure of 22 American embassies across the Muslim world was similar to the warnings the United States had received before the Sept 11, 2001 terrorist attack but ignored.

On Saturday afternoon, US national security advisers met at the White House to discuss the nature of the threat. The White House said Secretary of State John Kerry, Secretary of Defence Chuck Hagel, and National Security Adviser Susan Rice attended this meeting.

Other attendees included US President Barack Obama’s chief of staff, Denis McDonough, Chairman of the Joint Chiefs of Staff Martin Dempsey, Homeland Security Secretary Janet Napolitano, Director of National Intelligence James Clapper, and the heads of the FBI and CIA.

“There is a significant threat stream, and we are reacting to it,” Gen Dempsey said at “ABC This Week” news show. The threat came from an “Al Qaeda branch,” he said.

“This is probably one of the most specific and credible threats I’ve seen perhaps since 9/11,” House Homeland Security Committee Chairman Michael McCaul told CBS News.

Senator Saxby Chambliss, the top Republican on the Senate Intelligence Committee, told Fox News the threat was “very reminiscent of what we saw pre-9/11.”

Besides closing its embassies across the Muslim world, the Obama administration has also issued a worldwide travel alert, warning Americans that Al Qaeda might target US citizens as well, particularly in the Middle East and North Africa.

The warning urged them to avoid travelling abroad in August as the terrorists were planning to attack American people and interests during this month.

After the Saturday afternoon meeting, the White House issued a statement, saying that President Obama had “instructed his national security team to take all appropriate steps to protect the American people in light of a potential threat occurring in or emanating from the Arabian Peninsula”.

The president’s top security advisers met to “further review the situation and follow-up actions”, the statement added.

Congressman Peter King of the House Intelligence Committee told ABC News that the threat was very specific “as to how enormous it would be” as well as to when it would happen.”

But “it didn’t specify where it’s going to be. And, you know, the assumption is that it’s probably most likely to happen in the Middle East at or about one of the embassies,” he added.

The congressman also warned Americans travelling abroad that “there’s no guarantee at all” that the terrorist would only attack targets in the Middle East.

“It could basically be in Europe; it could be in the United States; it could be a series of combined attacks,” he said.

About half a dozen Republican lawmakers, who appeared in various television shows on Sunday, praised the country’s Democratic administration for taking pre-emptive measures.

“The administration’s call to close these embassies was actually a very smart call, particularly in light of what happened in Benghazi,” Mr McCaul said, referring to the fatal 2012 attack on a US outpost in Benghazi, Libya.

Fox News quoted US security officials as saying that the chatter picked up over the past two weeks exceeded anything in the last decade. And it included Al Qaeda leader Ayman Al-Zawahiri demanding that key leaders of the terror network in the Arabian Peninsula step up their activities in the wake of recent killings of top terrorists.

A senior US official told The Chicago Tribune that the United States had “forces prepared for some time to respond to potential contingencies in the Middle East and North Africa.”

“We’re postured to support timely and effective action if requested. This latest threat is serious, and the Pentagon is working closely with its partners … to confront it,” the official added.

Although President Obama was at the Camp David presidential retreat on Sunday to celebrate his birthday, he was receiving regular briefings about the potential threat and US preparedness measures, the White House said.

Susan Rice and US counter-terrorism adviser Lisa Monaco briefed him after the high-level meeting on Saturday as well, it added.

CBS News reported that intelligence officials had information about a major plot.

“Intelligence officers have reporting from a reliable source that a major plot is under way and that the team to carry it out has been selected and is in place,” CBS said. US authorities did not know the date, the timing or the target of the planned attack, it said.

France said earlier on Saturday it would close its embassy in Yemen for several days from Sunday, following similar moves by Britain and Germany.