US President Barack Obama has cleared the bill to provide $225m additional funds to Israel to support the Iron Dome anti-missile defence system.
The bill was approved by the US Congress on Friday with the Senate adopting it through a voice vote and the House of Representatives voting for it 395-8.
Obama has signed the bill immediately after Congress' approval to enable overnight transfer of the funds to Israel, ABC News reported.
US Senator John McCain said: "This isn't just about money. It is a signal from the American people and the American taxpayer that we are with the Israelis because if we, they do not have iron dome, they can't defend themselves."
The US Department of Defense placed the request for additional funding with the Congress last month, to accelerate the production of Iron Dome components in Israel and maintain adequate stockpiles for the system.
Built by Rafael Advanced Defense Systems, Iron Dome is claimed to have intercepted 556 of the 2,560 rockets launched by the Hamas militants since the start of the Operation Protective Edge on 8 July.
Meanwhile, Israel is implementing a seven-hour ceasefire today, after a 72-hour peace truce failed on Friday. The country has, however, said that the ceasefire would not be effective in the southern town of Rafah.
At least ten Palestinians were killed in an Israeli air strike at a United Nations Relief and Works Agency (UNRWA) school in Rafah on Sunday.
UN Secretary-General Ban Ki-moon said: "United Nations shelters must be safe zones not combat zones.
"This attack, along with other breaches of international law, must be swiftly investigated and those responsible held accountable. It is a moral outrage and a criminal act."
The Israeli military has said it had targeted three Hamas militants near the school.
Image: Palestinian families seek shelter at an UNRWA school after leaving their homes in the Gaza Strip. Photo: courtesy of UNRWA.