WASHINGTON (AFP) – US Secretary of State Hillary Clinton warned Monday that instability in Yemen, where the United States has closed its embassy over fears of an Al-Qaeda strike, threatens regional stability.

Word of a possible attack by the fundamentalist group prompted Washington to close its embassy in the Yemeni capital on Sunday. The British and French authorities followed suit, while Japan suspended consular services at its embassy.

“The instability in Yemen is a threat to regional stability and even global stability,” Clinton told reporters following talks with Qatari Prime Minister Sheikh Hamad bin Jassem bin Jabr al-Thani.

“And certainly, we know that this is a difficult set of challenges, but they have to be addressed.”

She noted that Washington was working closely with its allies to chart “the best way forward” to address the security concerns.

The United States will reopen its embassy in Yemen “when the conditions permit,” the chief US diplomat added, noting security was under constant review.

Long-standing concerns that Yemen has become a haven for Islamic terror groups were thrown into sharp relief when a Nigerian man allegedly trained in Yemen was charged with trying to blow up a US airliner on December 25.

Umar Farouk Abdulmutallab, 23, reportedly confessed to being trained by an Al-Qaeda bombmaker in Yemen for his alleged mission to blow up the plane as it came into land in Detroit, sparking a major international security scare.

President Barack Obama has revealed that Abdulmutallab spent time in Yemen during the summer where he was allegedly in contact with Al-Qaeda in the Arabian Peninsula (AQAP).

Clinton noted the State Department was reviewing whether to revise procedures that allowed Abdulmutallab to board the Amsterdam-Detroit flight.

“Based on what we know now, the State Department fully complied with the requirements set forth in the inter-agency process as to what should be done when information about a potential threat is known,” she said.

“But we’re looking to see whether those procedures need to be changed, upgraded.”

Washington has noted that Abdulmutallab, the son of a wealthy Nigerian banker, was added to a watchlist of some 550,000 names last month after his father warned US officials in Abuja about his son’s increasing radicalism.

But he was not added to the no-fly list, meaning he was able to use his multiple-entry, two-year visa obtained from the US embassy in London in June 2008 to fly from Lagos to Amsterdam, then on to Detroit on Christmas Day.