An expected Israeli assault on Rafah has aid groups scrambling for ways to help the 1.5 million civilians sheltering in the south Gaza city, but the uncertain timeline poses a logistical nightmare.

"We always are prepared with plans to upscale or downscale but, really, we don't know what to expect," said Bushra Khalidi, head of advocacy at Oxfam.

Oxfam joined 12 other aid groups in a joint call for a cease-fire on April 3, stressing that more than a million civilians, including at least 610,000 children, were "in direct line of fire" in Rafah.