Under the terms of the two-year-old agreement, Tehran scaled back production of nuke-making material in return for massive sanctions relief.
The Trump administration faced a new congressional deadline Monday to say whether Iran has curbed its nuclear weapons program in line with the accord.
"The conditions," according to one official who the White House would not name publicly, "have been met, based on information available to the United States."
The 2015 agreement rests on a series of technical benchmarks, and was seen in Washington as a way of avoiding military action to prevent Iran from getting a nuke.
But it has not relieved tensions between Tehran and Washington, which continue to clash particularly over conflicts in the Middle East like Syria and Yemen, where Iran-backed militias hold clout.
During his election campaign Trump denounced the Obama-era deal, promising to renegotiate it and vowing to get tough on Iran.
Trump has now twice affirmed Iran's compliance since taking office -- effectively keeping the deal in place.
But the White House took pains to stress it was not going soft on Iran, pointing to new non-nuclear sanctions and stricter implementation of the deal.
An official added: "we do expect that we will be implementing new sanctions that pertain to Iran's ballistic missile program and fast boat program."
"Iran remains one of the most dangerous threats to US interests and regional stability," the official said.
Many in Trump's cabinet tangled with Iran-backed militias during the US occupation of Iraq.
Ex-Marines like Homeland Security Secretary John Kelly and Defense Secretary Jim Mattis also keenly remember Iran-backed Hezbollah's attack on the corps barracks in Lebanon in 1983.
Top among the list of concerns today are improved Iranian missile capabilities, support for the Syrian government, human rights abuses and the detention of Americans.
Xiyue Wang, a 37-year-old Chinese-American researcher at Princeton University, was recently sentenced to 10 years in Iranian prison.
"The president and the secretary of state judge that these Iranian activities severely undermine the intent of the (agreement), which was to contribute to regional and international peace and security," one official said.
"As a result the president and the secretary of state and the entire administration judged that Iran is unquestionably in default of the spirit" of the accord, the official added.
For its part, Iran's complains of non-US compliance, accusing the US administration of failing to lift sanctions in line with the deal.
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