The Israeli Iron Dome missile defense system (left) intercepts rockets (right) fired by Hamas from northern Gaza in the sky above the Gaza Strip overnight on Sunday. Israel pummelled Gaza with air strikes, killing 10 members of an extended family and demolishing a building housing international media outlets, as Palestinian militants fired back barrages of rockets. Photo: AFP

A group of leftist US Democrats came under heavy fire Tuesday after reportedly vowing to nix a short-term spending bill over a $1 billion allocation for Israel's Iron Dome missile defense system.

The party leadership vowed there would be no interruption in funding, with the cash being sourced elsewhere - but not before being berated by Republicans for capitulating to "anti-Semites" on their left flank.  

Steny Hoyer, the Democratic House of Representatives majority leader, said there would be a vote "before the end of this week that will fund fully Iron Dome."

He added he had talked to Israeli Foreign Minister Yair Lapid "and assured him that that bill was going to pass this house."

He said the House would use an accelerated procedure known as a suspension bill that requires a bill be approved by two thirds of the members present, or a unanimous oral vote. The Senate will then have to adopt it.

Tuesday's drama was sparked by House Democrats removing a provision originally included in a bill to keep the federal government funded that would have helped boost the Israeli air defense system.

The about-face came after a group of leftist representatives objected to the allocation, US media reported, threatening to tank the bill when it comes up for a vote later Tuesday. 

While the row looked ultimately like a storm in a teacup, it underlined that progressives are becoming increasingly skeptical of no-strings-attached aid to America's key ally in the Middle East, just months after the end of hard-line right-winger Benjamin Netanyahu's 11-year premiership.

Operational for a decade, Iron Dome has intercepted and destroyed thousands of short-range rockets and artillery shells launched by Hamas militants from Gaza before they were able to hit populated areas, Israeli officials say.

House Republican leader Kevin McCarthy blasted Democrats for capitulating to "the anti-Semitic influence of their radical members," an accusation echoed by conservative Texas Senator Ted Cruz, who urged the Democratic rank-and-file to denounce the party's leadership.