WASHINGTON —Saudi Arabiahas told the Obama administration and members of Congress that it will sell off hundreds of billions of dollars’ worth of American assets held by the kingdom if Congress passes a bill that would allow the Saudi government to be held responsible in American courts for any role in the Sept. 11, 2001, attacks.

The Obama administration has lobbied Congress to the bill’s passage, according to administration officials and congressional aides from both parties, and the Saudi threats have been the subject of intense discussions in recent weeks between lawmakers and officials from the State Department and the Pen***on. The officials have warned senators of diplomatic and economic fallout from the legislation.

Adel al-Jubeir, the Saudi foreign minister, delivered the kingdom’s message personally last month during a trip to Washington, telling lawmakers that Saudi Arabia would be forced to sell up to $750 billion in treasury securities and other assets in the United States before they could be in danger of being frozen by American courts.

Several outside economists are skeptical that the Saudis will follow through, saying that such a sell-off would be difficult to execute and would end up crippling the kingdom’s economy. But the threat is another sign of the escalating tensions between Saudi Arabia and the United States.

The administration, which argues that the legislation would put Americans at legal risk overseas, has been lobbying so intently against the bill that some lawmakers and families of Sept. 11 victims are infuriated. In their view, the Obama administration has consistently sided with the kingdom and has thwarted their efforts to learn what they believe to be the truth about the role some Saudi officials played in the terrorist plot.