On the eve of an important meeting of the UN Security Council, the charity organization Save the Children criticized the failed efforts of international leaders to ensure a permanent ceasefire in Gaza, Sky News reports.

“This short pause will end on Wednesday, and without a ceasefire, the children of Gaza will have to live through the nightmare again,” the charity said in a statement.

At least 6,000 children have been killed in Gaza since the conflict began, according to the health ministry of the Hamas-run enclave.

But Save the Children says the actual number of children killed to date is likely to be higher.

“Given the challenges in collecting and verifying casualty data since November 11 due to the breakdown of communications and hospital services in Gaza, the reality is likely to be worse,” the statement said.

He added: “A further 4,400 children are believed to be missing, likely buried under the rubble.”

The failure of the international community to agree on a ceasefire is costing thousands of lives, the charity concluded.