ACCRA: The Obama administration is readying new sanctions on Syrian President Bashar Assad's regime and its allies.

Senior officials travelling with US Secretary of State Hillary Rodham Clinton as she wraps up a nine-nation tour of Africa say that fresh sanctions aimed at hastening Assad's ouster are imminent.

The officials spoke on Friday on condition of anonymity because they were not authorised to preview the move.

Clinton is heading to Istanbul for weekend talks with top Turkish officials and opposition activists. The sanctions will complement existing penalties already imposed.

The talks in Turkey will focus on forming a "common operational picture" to guide a democratic transition in post-Assad Syria.