By Patricia Zengerle and Mark Hosenball
WASHINGTON (Reuters) - Forces seeking to oust Syrian President Bashar Al Assad are gaining strength and territory, but the Syrian opposition remains fragmented and is grappling with an infusion of militant foreign fighters, Director of National Intelligence James Clapper said on Tuesday.
Two years into an uprising against Assad's rule, U.S. intelligence agencies do not know how long the Syrian leader will keep his hold on the country, Clapper said at a Senate Intelligence Committee on global security threats.
"The question comes up, 'How long will Assad last?' And our standard answer is, 'His days are numbered. We just don't know the number.' Our assessment is that he is very committed to hanging in there and sustaining his control of the regime," Clapper told the Senate panel.
Assad's government is losing territory and experiencing shortages in manpower and logistics, Clapper said. But at the same time, there are "literally hundreds" of cells of opposition fighters over which leaders are struggling to impose more centralized command and control.
Clapper noted a growing presence among Assad's opponents of foreign fighters, many associated with the Nusra Front, an offshoot of al Qaeda in Iraq that has gained strength in Syria partly by offering services to a population beaten down by two years of civil war.
"They are, where they can, providing more and more municipal services in what is a very terrible situation from a humanitarian standpoint," Clapper said.
U.S. and European officials have recently said that their governments will be stepping up efforts to provide "non-lethal" aid and training to non-Islamist rebel factions fighting Assad.
Officials have also privately indicated that some training of rebels, with support and possible limited participation of Americans, is going on in neighboring countries.
But U.S. and other Western personnel on the scene are equally, if not more, concerned about tracking the growing influence and activities of Nusra Front and other militants.
They also want to ensure they do not get their hands on weapons that could threaten western interests, including surface-to-air missiles capable of bringing down aircraft and chemical weapons which Assad's regime is believed to have stockpiled.
The United States and its allies are trying to keep close track of Syria's arsenal of suspected chemical and biological warfare agents. Clapper noted U.S. intelligence agencies' concern that Assad's government "might be prepared to use chemical weapons" against his own people and that outside groups could gain access to them.
He added that Iran is doing what it can to prop up Assad's government, through aid and training, despite being weakened by international sanctions seeking to keep Tehran from developing nuclear weapons capability.
"Iran continues to be a destabilizing force in the region providing weapons and training to Syrian forces and standing up a militia force there to fight the Syrian opposition," Clapper said, with the goal of having at least a foothold in Syria even if Assad falls.
(Editing by Cynthia Osterman)