The Obama administration has invited the head of the newly recognised Syrian rebel coalition, Moaz al-Khatib, to Washington as the US attempts to build a sympathetic administration to slot into place and keep hostile Islamist forces at bay when President Bashar al-Assad falls.

The invitation to Khatib came at a meeting in Morocco of western and Arab nations backing the Syrian uprising at which the US gave formal recognition to the Syrian National Coalition for Revolutionary and Opposition Forces as the "legitimate representative of the Syrian people".

The US move has been criticised as belated and insufficient, in part because of Washington's hesitation to supply weapons to the coalition while more radical groups in Syria, including an al-Qaida affiliate declared a terrorist organisation by Washington on Tuesday, are evidently armed by Qatar and Saudi Arabia.