National Security Council spokesman John Kirby says the call for a cease-fire right now "only benefits Hamas."
This comes as Israel is escalating its bombardment of targets in the Gaza Strip ahead of an expected ground invasion against Hamas militants.
The war is rapidly raising the death toll in Gaza, and the U.S. fears the fighting could spark a wider conflict in the region.
Gaza’s 2.3 million people have been running out of food, water and medicine since Israel sealed off the territory following the Hamas attack on Israeli towns on October.
The aid convoys allowed into Gaza so far have carried a fraction of what's needed, and the U.N. said distribution will have to stop if there's no fuel for the trucks.
The U.N. health agency on Tuesday called for an immediate humanitarian cease-fire in Gaza to be able to distribute fuel and essential, life-saving health supplies, including to major hospitals in the strip’s northern half.