"You are witnessing the single greatest WITCH HUNT in American political history", the President wrote on Twitter.
Democratic Sen. Sherrod Brown, one of the bill's cosponsor, told reporters on Wednesday that the White House was already beginning to lobby against the measure. John McCain of Arizona, the Republican chairman of the Armed Services Committee, said ahead of the vote.
During the hearing Wednesday, Secretary of State Rex W. Tillerson urged senators to oppose the measure so that Trump and his administration would have "the flexibility to turn the heat up" if necessary. The inquiries raised red flags among Obama administration holdovers at the State Department, who asked Congress to preempt any attempts by Trump to alter the sanctions regime now in place.
The president, who has been highly critical of Iran, would have to reject the tougher sanctions against Tehran if he rejected other parts of the legislation. "But this bill is a conspicuous exception to that", said Senate Majority Leader Mitch McConnell, Kentucky Republican. Once the Iran bill passes the Senate, the legislation moves to the House for action.
It was introduced amid an intense focus in the United States capital on relations with Russian Federation and an investigation into whether Mr Trump's associates colluded with Moscow to influence the 2016 election.
The Iran bill could come up for a vote as soon as this week.
Idaho Republican Senator Mike Crapo helped push legislation through the Senate Wednesday to maintain and expand sanctions against the government of Russian Federation.
The discussions gathered steam late last month after Sen.
"The United States needs to respond to Iranian and Russian aggression with strength", Wicker said. Congressional committees and the FBI are investigating the Russian interference and whether there was any collusion with Trump's campaign.
House and Senate committees are investigating Russia's meddling and potential links to the Trump campaign, with testimony scheduled on Tuesday from Attorney General Jeff Sessions. Special Counsel Robert Mueller is conducting a separate probe.
A statement from Republican and Democratic leaders on the Senate banking committee said the amendment "expands sanctions against the government of Russian Federation in response to the violation of the territorial integrity of the Ukraine and Crimea, its brazen cyber attacks and interference in elections, and its continuing aggression in Syria".
The fresh sanctions would also see Russian mining, metals, shipping and railways affected, with the Senate also planning on putting into law some previous sanctions touching Russian energy projects and debt financing.
Under the legislation, new sanctions could be levied on entities engaging in "malicious cyber activity".
Today's vote was the most significant blow the Republican President has received from the Republican Congress.
The power would allow congress to strengthen those sanctions in retaliation for Moscow's alleged interference in the 2016 election and its actions in Syria.