Washington DC - Left-wing Democratic lawmakers have called on the US to break its silence on Israel's suspected nuclear weapons program, shattering a decades-long bipartisan reticence in Washington on the sensitive issue.

Israel is widely believed to have developed nuclear weapons in the 1960s but keeps a deliberately ambiguous policy by neither confirming nor denying its arsenal, which is not subject to any international monitoring.

Some 30 Democratic lawmakers led by Representative Joaquin Castro said that the US needed clear answers after President Donald Trump joined Israel in a war against Iran, launched in part over charges that Tehran has been seeking to build a weapon through its nominally civilian nuclear program.

"We cannot develop coherent nonproliferation policy for the Middle East, including with respect to Iran's civil nuclear program and Saudi Arabia's civil nuclear ambitions, while maintaining a policy of official silence about the nuclear weapons capabilities of one party central to the ongoing conflict in which the United States is a direct participant," they wrote in the letter made public late Wednesday.

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"We ask that you hold Israel to the same standard of transparency that the United States expects from any other country that may be pursuing or retaining nuclear weapons capability."

The lawmakers asked Secretary of State Marco Rubio to reply by May 18 to explain Israel's nuclear capabilities as well as its nuclear doctrine, including whether Israel could use the ultra-destructive weapons in Iran.

They also asked for an assessment of risk for US citizens of any future Iranian strike on Israel's secretive Dimona nuclear research center. Iranian missiles injured dozens nearby in March, stunning residents of the tightly guarded desert town.

It is highly unlikely the administration will respond on Israel's nuclear program, on which administrations across party lines have long refused to comment.

In 2006, then Defense Secretary Robert Gates indirectly appeared to confirm Israel's nuclear program in testimony to Congress while discussing Iran.

After the October 7, 2023 Hamas attack on Israel, a far-right Israeli minister said the country could drop a nuclear bomb on Gaza, a comment from which Prime Minister Benjamin Netanyahu distanced himself.

Prominent Democrats who signed the letter include representatives Alexandria Ocasio-Cortez and Ro Khanna.

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The intervention comes amid escalating criticism of Israel from Democrats.

The party has almost universally condemned Trump's decision to join the Iran war, with many lawmakers saying their former president Joe Biden should have been tougher on Israel over its relentless military campaign in Gaza, which has been deemed a genocide by numerous experts and human rights groups.