The UN's Relief and Works Agency (Unrwa) halted aid on Thursday, saying Hamas had taken hundreds of tonnes of aid from shipments of flour and rice.
An Unrwa spokesman said deliveries were not expected to resume until after Tuesday's Israeli elections.
The Gaza Strip is facing a humanitarian crisis following Israel's recent three-week offensive.
About half of Gaza's population is dependent on UN food aid.
Israel intensified a blockade on the Gaza Strip 19 months ago when Hamas took over the territory.
The lifting of the blockade is among Hamas' demands for agreeing a long-term truce with Israel.
Though Unrwa said it could resume aid deliveries, it said its efforts to give aid to 900,000 Gaza residents continued to be hampered by Israel's refusal to let in supplies used for making the plastic bags in which aid is packaged.
The agency said it had also been denied permission to bring in 12 lorry-loads of paper to print human rights textbooks, and another five lorries carrying exercise books for 200,000 children.
Last week, aid supplies were diverted twice.
Two days before the seizure of flour and rice, 3,500 blankets and more than 400 food parcels were seized at gunpoint from a distribution centre in Gaza, the UN said.
It had said that aid would only resume if Hamas gave assurances that such seizures would not happen again.
Hamas admitted a "mistake" and said it would return the supplies.
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