WASHINGTON, D.C. — A group of 30 House Democrats sent a letter on Monday to Secretary of State Marco Rubio requesting that he publicly acknowledge that Israel possesses nuclear weapons. The letter was led by Representative Joaquin Castro, a Texas Democrat.

The letter asked that "Israel be held to the same standard as any other foreign country, and that the United States government speaks candidly about its potential nuclear weapons capabilities, whatever they may be." Israel has never acknowledged its nuclear weapons programs, and no U.S. administration has publicly stated that such a program exists.

The United States openly acknowledges the nuclear weapons programs of the United Kingdom, France, India, Pakistan, Russia, China and North Korea. The letter from Castro and his colleagues argued that Israel should receive the same candid treatment from the U.S. government as those countries.

Israel's nuclear weapons program traces its origins to the 1950s, with assistance from allies including France and apartheid South Africa. The program has never been formally confirmed by the Israeli government.

At a congressional hearing in March, Thomas DiNanno, the under secretary of state for arms control and international security, said he could not answer when asked to detail Israel's nuclear capabilities. DiNanno's response illustrated the long-standing U.S. practice of declining to comment publicly on Israel's nuclear status.

Early in his presidency, former President Barack Obama said he did not wish to speculate about Israel's nuclear weapons programs. Obama's position was consistent with that of previous administrations, which have also refrained from publicly addressing the matter.