GENEVA, March 4 (Reuters) - A humanitarian convoy carrying life-saving supplies from U.N. and other aid agencies will not enter the besieged Syrian enclave of eastern Ghouta as planned on Sunday, a U.N. official in Syria told Reuters.

"The convoy to east Ghouta is not able to proceed today," the official said, adding that the U.N. and its humanitarian partners "remain on standby to deliver desperately needed assistance as soon as conditions allow".

The convoy of some 40 trucks had been due to go to Douma in the government-besieged enclave near Damascus, where some 400,000 people need food, medical and other supplies, the U.N. says. Only one small convoy with supplies for 7,200 people has been allowed to Ghouta so far this year, in mid-February. (Reporting by Stephanie Nebehay editing by Alexander Smith)