State Department spokesman Tom Casey said the sanctions showed that Iran was becoming "increasingly isolated" and the international community was "serious about increasing the pressure on them" for ignoring UN resolutions.
"Certainly we would like to see Iran choose the other path and suspend its enrichment related activities and come to the negotiating table," Casey said.
"Ultimately though, absent that, we expect to see increased forms of diplomatic pressure and this action by the EU is part of it and certainly welcomed by us."
The new sanctions, which notably ban Iran's largest bank, Bank Melli, from operating in Europe, were approved during a meeting of EU agriculture and fisheries ministers in Luxembourg.
The measures also add another 20 individuals and 15 organizations to the EU's visa-ban and assets-freeze lists.
The EU move, running alongside a string of UN sanctions against Iran adopted since 2006, aims at persuading Tehran to suspend its uranium enrichment activities, which the international community fears are part of a nuclear weapons building program.
Tehran insists it wants atomic energy only for a growing population whose fossil fuels will eventually run out.
Washington has been waiting for Europe to take such measures for months, and the matter became a theme of US President George W. Bush's recent European tour.
The 27 EU member states have been working out the details since May but the measures were delayed until after a trip to Iran earlier this month by EU foreign policy chief Javier Solana.
