ROME (Reuters) - Western and Arab officials will meet representatives of the Syrian opposition in Istanbul next Monday to discuss military and humanitarian support for rebels fighting President Bashar al-Assad, a European diplomatic source said on Thursday.

"The meeting aims to work directly with opposition structures to increase the level of support," the source said, adding that both civilian and military representatives of the Syrian opposition would attend.

The source spoke on the margins of a meeting in Rome between the Syrian National Coalition - the main civilian opposition group - and Western and Arab nations.

In a policy shift, the United States has decided to provide medical supplies and food to Syrian fighters, but will still oppose giving the rebels weapons, a source familiar with the matter said overnight.

(Reporting by Khaled Oweis, Editing By Barry Moody)