WASHINGTON - Despite some military defections, Syrian President Bashar Assad's inner circle remains cohesive and the 16-month conflict with rebels is likely to be a drawn-out struggle, senior US intelligence officials said on Tuesday.

That assessment appears to dash any US hopes that Assad, whose ouster Washington has called for, will fall soon of his own accord. The Obama administration has declined to intervene militarily in Syria, citing the lack of international backing and the country's sectarian divisions.

White House spokesman Jay Carney said on Tuesday that Assad "has been slowly, too slowly, losing his grip over his country. The process, because of his refusal to step aside, has been horrific and has exacted a terrible toll on the Syrian people."

But US intelligence agencies, watching closely for cracks in Assad's inner circle, do not see them so far.

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