At a summit in Brussels, Nicholas Burns called Iran “the major disruptive, negative force in the Middle East”.
The five permanent Security Council members plus Germany are to meet on Tuesday to discuss a sanctions package.
The council recommended sanctions after Iran failed to comply with a deadline for refusing to end uranium enrichment.
However, France indicated that the six powers were nearing an agreement on the wording of a UN resolution.
Talks between Foreign Minister Philippe Douste-Blazy and his Russian counterpart Sergei Lavrov ended in broad consensus, Mr Douste-Blazy said in Brussels.
He said he hoped the final resolution could be agreed at the talks in Paris on Tuesday.
Criticism
Speaking to reporters at the meeting of the Organisation for Security and Co-operation in Europe (OSCE), Mr Burns, an under secretary of state, criticised Iran over more than its nuclear programme.
“We have to speak truthfully about Iran. It is the major disruptive, negative force in the Middle East.
“Think about what we stand for in the Middle East: we want to see the Israelis and the Palestinians find peace, a two-state solution. We want to see Lebanon free and independent. We want to see Iraq free of terrorism.
“What does Iran stand for? Iran stands for disrupting states, disrupting peace and solving everything through the barrel of a gun.”
Mr Burns called on Russia and China, the two permanent Security Council members so far reluctant to publicly endorse sanctions against Iran, to support the move.
“It’s been too long we have been debating… we have to pass the sanctions resolution,” he said.
Wording debate
The UK, France and Germany have drafted a resolution proposing restrictions on trade with Iran that would help its nuclear or missile work.
Financial and travel restrictions on individuals in the nuclear and missile fields are also thought to be on the list.
Russia and to a lesser extent China have tried to water down the text, saying the sanctions should not target individuals and should be limited in duration.
Correspondents say Washington wants to harden at least the wording of the text.
