Speaking at a hearing of the House Committee on Homeland Security titled "Iranian Terror Operations on American Soil," Chairman Peter King (Republican-New York) said Tehran's alleged actions amounted to "an act of war."
"So you have the assassination of a foreign ambassador, you have the willingness to kill hundreds of Americans -- this is an act of war," King said.
"I don't think we can just do business as usual or even carry out sanctions as usual."
Another Republican lawmaker on the committee, Michael McCaul (Texas), said that if the plot was approved at the highest levels of the Iranian government, then military force against Iran should be considered.
Democrats called for a more measured approach, with top committee Democrat Bennie Thompson (Mississippi) warning, "We must not overstate nor overreact to the threat we currently face from Iran."
Another Democratic lawmaker on the committee, Jackie Speier (California), said Iran must be held accountable, but that the United States didn't want and could not afford to "open another front in the war on terror."
The alleged plot, announced by U.S. officials on October 11, has prompted pledges by the Obama administration to increase pressure on Tehran, including possibly putting sanctions on its Central Bank.