The attempted bombing of a US passenger jet in Detroit has highlighted the growing prominence of al-Qaeda in Yemen and the expanding role of the US military and intelligence agencies in the region.
Civil war and lawlessness have turned the Arab world's poorest state into an attractive alternative base for al-Qaeda, as the US increases its troop presence in Afghanistan and bordering areas.
The 23-year-old man charged in connection with the Christmas Day attack in Detroit, Umar Farouk Abdulmutallab, has told investigators that al-Qaeda operatives in Yemen supplied him with the explosive device and trained him on how to detonate it.
The al-Qaeda wing in Yemen has gained ground over the last year and Washington fears the state could become a central base of operations outside Pakistan and Afghanistan, according to US defence and counterterrorism officials.
Against this backdrop, the US has quietly been supplying military equipment, intelligence and training to Yemeni forces, who raided suspected al-Qaeda hide-outs this month.
Al-Qaeda alleges that US jets participated in those attacks.
US officials have declined to comment on whether US aircraft, including unmanned drones, took part in the raids.
The US Defence Department has so far provided Yemen with some $67m in overt counterterrorism assistance in 2009, a figure that does not include covert programs run by US special forces and the CIA.
Even so, the Pentagon has proposed expanding that overt assistance program in fiscal 2010 but defence officials declined to provide a dollar-figure or details.
'Yemen has a growing al-Qaeda threat and the government there has taken important steps to address it,' Pentagon spokesman Bryan Whitman said when asked about Yemen's arrest of 29 suspected al-Qaeda members this month.
Senator Joseph Lieberman, chairman of the Homeland Security Committee, admitted yesterday that the US has a 'growing presence" in Yemen which included Special Operations, Green Berets and intelligence agencies.
Mr Lieberman, who recently visited the Yemeni capital Sanaa, said a US official there told him that 'Iraq was yesterday's war. Afghanistan is today's war. If we don't act pre-emptively, Yemen will be tomorrow's war.'
Yemen has been a long-standing base of support for al-Qaeda.
Militants bombed the Navy warship USS Cole in the Yemeni port of Aden in 2000, killing 17 US sailors. And Yemenis were one of the largest groups to train in al-Qaeda's camps in Afghanistan before the 11 September attacks in 2001.
Besides battling al-Qaeda, Yemen is fighting Shia rebels in the north and separatist sentiment in the south.
Fearing instability in Yemen could turn into a security threat for its kingdom, Saudi Arabia, the world's biggest oil exporter, began attacking Yemen's Shia rebels, known as the Houthis, in early November.
