Former US President has accused his successor Joe Biden of "indirectly" funding the Hamas attack on Israel.
"These Hamas attacks are a disgrace and Israel has every right to defend itself with overwhelming force," Donald Trump said in a statement.
"Sadly, American taxpayer dollars helped fund these attacks, which many reports are saying came from the Biden Administration," he alleged.
Trump's allegations back Republican claims that $6 billion released last month to Iran as part of a prisoner exchange deal was used to fund the Hamas attack.
White House Deputy Press Secretary Andrew Bates said on social media that "this is a shameful lie in every respect, at a time when both parties should be totally united in supporting Israel's defense."
The money "can only be used for verifiable purchases of humanitarian needs like food and medicine," Bates added, in a fierce retort.
There seemed little chance of keeping US partisan politics out of the matter, with the senior administration official saying that the situation in Congress - where the lower chamber currently lacks a leader - will likely complicate any US action.
The Israel-Palestine conflict's bloodiest escalation in decades saw Hamas carry out a massive rocket barrage and ground, air and sea offensive, that Israel's army, said had killed more than 300 Israelis and wounded 1,000. Gaza officials said intense Israeli air strikes on the coastal enclave had brought the Palestinian death count to at least 232, with nearly 1,700 wounded.
Hamas fighters fired thousands of rockets and breached Gaza's security barrier, attacking nearby Israeli towns and military posts. They also opened fire on residents and passersby. The group labelled its attack "Operation Al-Aqsa Flood" and called on "resistance fighters in the West Bank" as well as in "Arab and Islamic nations" to join the battle. Hamas chief Ismail Haniyeh said the group was on the "verge of a great victory".
In response to the deadly attacks, the Israel defense forces also declared a "readiness for war".
"The IDF (army) is about to use all its force to destroy Hamas's capabilities. We'll strike them to the bitter end and avenge with force this black day they brought on Israel and its people," said Israel Prime Minister Benjamin Netanyahu.
Track Latest News Live on NDTV.com and get news updates from India and around the world