The US government must immediately end its ongoing deliveries of large quantities of arms to Israel, which are providing the tools to commit further serious violations of international law in Gaza, said Amnesty International, as it called for a total arms embargo on all parties to the conflict.

The call comes amid reports that the Pentagon has approved the immediate transfer of grenades and mortar rounds to the Israeli armed forces from a US arms stockpile pre-positioned in Israel, and follows a shipment of 4.3 tons of US-manufactured rocket motors, which arrived in the Israeli port of Haifa on 15 July.

These deliveries add to more than US$62 million worth of munitions, including guided missile parts and rocket launchers, artillery parts and small arms, already exported from the USA to Israel between January and May this year.

“The US government is adding fuel to the fire by continuing its supply of the type of arms being used by Israel’s armed forces to violate human rights. The US government must accept that by repeatedly shipping and paying for such arms on this scale they are exacerbating and further enabling grave abuses to be committed against civilians during the conflict in Gaza,” said Brian Wood, Head of Arms Control and Human Rights at Amnesty International.

Palestinian armed groups have continued to fire rockets indiscriminately into Israel, endangering civilians in flagrant violation of international law. Amnesty International has repeatedly called for an immediate end to such attacks, which amount to war crimes.

Last week the speaker of the Iranian parliament said Iran had provided arms manufacturing know-how to Hamas in Gaza. In November 2012 he said Iran had given both financial and military support to Hamas and the Commander of Iran’s Revolutionary Guards said missile technology has been supplied. Hamas fighters have admitted to firing Iranian-type Fajr 5 missiles towards Tel Aviv, but mostly fire shorter-range M25 or “Qassam” rockets.

The USA is by far the largest exporter of military equipment to Israel. According to data made public by the US government, its arms transfers to Israel from January to May 2014 included nearly $27million for “rocket launchers”, $9.3 million worth in “parts of guided missiles” and nearly $762,000 for “bombs, grenades and munitions of war”.

Since 2012, the USA has exported $276 million worth of basic weapons and munitions to Israel, a figure that excludes exports of military transport equipment and high technologies.

The news on 30 July that the USA had allowed the resupply of munitions to Israel came the same day the US government condemned the shelling of a UN school in Gaza which killed at least 20 people, including children and UN humanitarian workers.

“It is deeply cynical for the White House to condemn the deaths and injuries of Palestinians, including children, and humanitarian workers, when it knows full well that the Israeli military responsible for such attacks are armed to the teeth with weapons and equipment bankrolled by US taxpayers,” said Brian Wood.

Amnesty International is calling on the UN to immediately impose a comprehensive arms embargo on Israel, Hamas and Palestinian armed groups with the aim of preventing violations of international humanitarian law and human rights by all sides.

In the absence of a UN arms embargo, the organization is calling on all states to unilaterally suspend all transfers of military equipment, assistance and munitions to all parties to the conflict. They should not resume until violations committed in previous conflicts are properly investigated with those responsible brought to justice.

“As the leading arms exporter to Israel, the USA must lead the way and demonstrate its proclaimed respect for human rights and international humanitarian law by urgently suspending arms transfers to Israel and pushing for a UN arms embargo on all parties to the conflict. By failing to do so it is displaying a callous disregard for lives being lost in the conflict on all sides,” said Brian Wood.

More than 1,400 Palestinians, mostly civilians, have been killed since Israel began its latest offensive in Gaza on 8 July. At least 56 Israeli soldiers have died in the conflict, as well as three civilians in Israel, including a Thai national.