US Secretary of State Hillary Clinton pushed back until Tuesday a planned trip to Morocco because of illness, a spokesman said.

"Because she has a stomach virus, our departure for Morocco has been moved from Monday to Tuesday. She will not have any schedule tomorrow in Washington," said Philippe Reines, a Clinton aide.

Clinton is to travel to Morocco, Tunisia and Abu Dhabi, capital of the United Arab Emirates, before taking part Wednesday in a meeting of the "Friends of the Syrian People" group.

The group is meeting to determine how to support Syria's opposition in its struggle against the regime of Bashar al-Assad.