UNITED NATIONS, April 30 (Reuters) - United Nations aid chief Martin Griffiths warned on Tuesday that despite global calls for Israel to spare Rafah in the Gaza Strip, "a ground operation there is on the immediate horizon."

He also said in a statement that Israeli improvements to aid access in Gaza "cannot be used to prepare for or justify a full-blown military assault on Rafah." (Reporting by Michelle Nichols; editing by Paul Grant)