US politicians mired in Washington gridlock agree on virtually nothing these days.

Nothing, it seems, apart from their unquestioned support for Israel.

A lopsided war has raged between Hamas militants firing rockets from the Gaza Strip, and the Israeli army which has launched a punishing air and ground offensive in an effort to halt the attacks.

More than 1000 Palestinians have been killed, mostly civilians, while 49 Israelis have died, mostly soldiers.

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With the death toll soaring, Israel has come in for harsh criticism in many parts of the world including Europe, where pro-Gaza demonstrations descended into anti-Semitic riots and an attack on a Jewish museum in Belgium left three dead, including two Israelis.

Not so in Washington.

The United States is Israel’s chief backer at the United Nations, where it routinely blocks Security Council resolutions condemning the Jewish state.

Washington has funnelled more than $US100 billion in aid to Israel since its formation in 1948, and consistently provides its chief Mideast ally with up-to-the minute weaponry.

A demonstrator at the United Nations finds a creative way to make her point.

Money to Israel flows through Congress largely uncontested – including now, with politicians signalling intention to commit $US225 million ($A243.44 million) for Israel’s Iron Dome missile defence shield.

In short, “America’s got Israel’s back,” US National Security Advisor Susan Rice assured a gathering of Jewish leaders Monday in Washington.

“We’ve always had a truly special relationship.”

Several politicians in attendance, including House Speaker John Boehner, each repeated the refrain in their own way.

“If there is a rocket on Israel, there is a rocket on America,” said congressman Kevin McCarthy, who next week becomes the number two House Republican.

Senators feuding over everything from budget bills to highway funding have united to unanimously pass a resolution backing Israel’s right to defend itself against “unprovoked rocket fire” by Hamas.

A similar measure unanimously passed the House of Representatives.

Why are Washington politicians in lock step with Israel?

Chief reasons include democratic principles, shared values, vocal evangelical Christians, and pressure from the powerful pro-Israel lobby.

The United States recognised Israel 11 minutes after it proclaimed independence, but the relationship was rocky in early years.

Washington disapproved of Israel’s invasion of Egypt in 1956 and refused to sell any major weapons to Israel until the 1960s.

But thanks to “a changing US containment and strategic posture (against the Soviet Union), US-Israeli relations grew by leaps and bounds after 1967,” wrote George Washington University political professor Michael Barnett.

Ever since, through bitter wars, deadly terror attacks, failed peace initiatives, and deeply controversial Jewish settlement expansions, Washington has sought to be a force for dispute resolution in the region.

Middle East stability was paramount, and Washington partnered accordingly with Israel to keep the region off the boil.

Most US presidents since 1948 have acknowledged the special relationship, but Rabbi William Gershon believes it is actually centuries old.

“I would argue it started back in 1654, when Jews came to this country and were very involved in supporting the American Revolution,” Gershon, president of the Rabbinical Assembly of the world’s Conservative movement, told AFP.

Early Jewish Americans embraced democratic principles, and the country’s Founding Fathers hewed closely to Hebrew traditions, rooting the modern republic on the Bible while insisting on religious tolerance.

Israeli Prime Minister Benjamin Netanyahu and US President Barack Obama in 2013.

Early pilgrims fleeing persecution in England described their arrival in the new world as a virtual re-enactment of the Exodus.

Many Americans, Gershon said, see the Jewish state embracing the same ideals and values that have come to define America.

“Israel being the only real democracy in the Middle East, I really do believe those bonds are strong, even when they do get strained, even when we disagree.”

American Christians provide a broad flank of support for Israel, arguing that the Holy Land has been part and parcel of Judaism – and by extension Christianity – for millennia.

“Our commitment to Israel is huge,” Pastor Paul de Vries, president of the New York Divinity School, told Jewish leaders.

Israel remains “the only country where Christians are free to worship in safety and liberty throughout the Middle East,” de Vries added.

With many conservative Republicans fuelled by an active Christian evangelical voter base, such politicians are among the most vocal supporters of Israel.

Adding no small amount of pro-Israel slant to Capitol Hill is the American Israel Public Affairs Committee, which has had great success in pushing through legislation it supports.

Critics and supporters alike see AIPAC as extraordinarily effective, and a National Journal survey of insiders ranked it the second most powerful lobbying group in Washington.

– AAP