WASHINGTON: Nearly 30 Democratic lawmakers have urged US Secretary of State Marco Rubio to end Washington’s longstanding ambiguity over Israel’s alleged nuclear weapons programme, arguing that such secrecy has become untenable during the ongoing war on Iran.

Israel is widely believed to be in possession of nuclear weapons, though it neither acknowledges nor denies having a nuclear arsenal.

In a May 4 letter addressed to Secretary Rubio, the lawmakers said the US was “currently engaged in a war against Iran, a conflict with nuclear dimensions that the administration has not adequately addressed with Congress or the American public”.

The move is led by Congressman Joaquin Castro, a senior Democratic lawmaker from Texas who has served in the US House of Representatives since 2013 and is known for his work on foreign policy and intelligence-related issues, including his tenure on the House Foreign Affairs Committee.

In a post on the social media platform X on Thursday, Castro said, “For nearly six decades, the US has voluntarily remained in the dark on Israel’s nuclear capabilities. The ambiguity ends now.

“There is too much at stake to accept ignorance. We are at war alongside Israel against Iran without knowing what their red lines are for using a nuclear weapon,” he said.

The letter repeatedly questioned the US government’s refusal to publicly acknowledge Israel’s alleged nuclear arsenal, while noting that multiple nuclear-armed states are directly involved in or affected by the conflict.

“The risks of miscalculation, escalation, and nuclear use in this environment are not theoretical,” the lawmakers warned, adding that Congress had a “constitutional responsibility to be fully informed about the nuclear balance in the Middle East”.

The lawmakers argued that “a policy of official ambiguity about the nuclear capabilities of one party to this conflict makes coherent nonproliferation policy in the Middle East impossible”.

The document is unusual because it openly presses the State Department to answer detailed questions about Israel’s alleged nuclear weapons capability, including warheads, launch systems, fissile material production, nuclear doctrine and possible thresholds for nuclear use.

“What nuclear weapons capability does Israel have?” the lawmakers asked directly. They also requested information on “any nuclear weapons systems that Israel fields, including warheads and launchers”.

The letter sought clarification on whether Israel possessed uranium enrichment capability and whether the Negev Nuclear Research Centre at Dimona produced fissile material or plutonium.

The lawmakers further asked whether Israel had communicated to US officials “any nuclear doctrine, red lines, or thresholds for nuclear use in the context of the current conflict with Iran”.

Another question asked: “Has the administration received any assurances from Israel that nuclear weapons will not be used?”

The lawmakers also sought to know whether there had been “any indications of Israel planning to use or deploy nuclear weapons during the recent Iran conflict or during other conflicts.”

The letter linked these concerns directly to the current war, noting that “The United States and Israel launched this war against Iran together on February 28, 2026.”

It added that “American and Israeli aircraft have conducted joint operations over Iran”, while decisions about ending the conflict were being made jointly. The lawmakers noted that Iranian missile strikes had targeted Dimona, saying the administration should assess the dangers of “radioactive harm to US citizens and personnel in the region” in the event of further attacks on Israeli nuclear facilities.

The letter also asked whether the administration had examined “what circumstances, including further Iranian strikes on Dimona or potential Israeli military setbacks, could lead Israel to consider nuclear use”.

The lawmakers cited a series of public statements and declassified US intelligence assessments to argue that Israel’s nuclear capability is already widely understood within official circles.

They referred to a 1974 Special National Intelligence Estimate that concluded that Israel “already has produced nuclear weapons”.

The letter also cited testimony given before Congress by former US defence secretary Robert Gates, who in 2006 said Iran was “surrounded by powers with nuclear weapons — Pakistan to their east, the Russians to the north, the Israelis to the west and us in the Persian Gulf”.

The lawmakers additionally referred to remarks by former Israeli prime minister Ehud Olmert, who in a 2006 interview listed Israel alongside “America, France, Israel, Russia” while discussing nuclear powers.

The document also mentioned Pakistan among the nuclear-armed states connected to the crisis. It noted that Pakistan signed a mutual defence agreement with Saudi Arabia in September 2025, while Riyadh itself had faced Iranian missile and drone attacks during the conflict.

The lawmakers argued that the involvement or proximity of multiple nuclear-capable states — including the United States, Britain, Russia, China, Pakistan, India, France and North Korea — made the current conflict exceptionally dangerous.

The letter concluded by questioning why senior State Department officials remain unable to publicly discuss Israel’s alleged nuclear capability. It cited testimony by Undersecretary of State Thomas DiNanno, who declined during a March 25 congressional hearing to answer questions on Israel’s nuclear status.

“What is the Department’s guidance to its employees on the discussion of any Israeli nuclear weapons capability?” the lawmakers asked.