The warning came as tensions heightened Tuesday between Moscow and Washington over possible punitive actions against Russian President Vladimir Putin's government for meddling in the US presidential election in 2016.
President Donald Trump's administration on Monday declined to take new steps against Moscow under a law designed to retaliate for election interference, drawing criticism from Democrats in particular.
Instead, Treasury publicly identified more than 100 Russian officials and business leaders eligible for sanctions.
The US State Department surprised observers by declaring it was not currently necessary to impose new sanctions under the law adopted last year, which it said already was acting as a deterrent.
And Treasury publicly identified more than 100 Russian officials and business leaders eligible for sanctions.
However, "In the near future, you'll see additional sanctions," Mnuchin said during Senate testimony. "In the next several months, maybe a month, I want to be careful in making that commitment."
"There was an extraordinary amount of work that went into this," Mnuchin said of the list of 114 people, including 96 "oligarchs" close to Putin each with estimated net worth of $1 billion or more.
"Our sanctions going forward will be based upon a lot of the work that the intelligence community did," he added. "We did not waive or delay."
The oligarchs list was submitted to Congress overnight. A Treasury spokesman confirmed the unclassified version of the list was derived from publicly available sources, including Forbes magazine.
(Except for the headline, this story has not been edited by NDTV staff and is published from a syndicated feed.)
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