The plan is to be detailed on Monday by the top United States diplomat, Secretary of State Mike Pompeo, in his first major foreign policy address since taking office in April.

"The US will be working hard to put together a coalition," State Department spokeswoman Heather Nauert told reporters.

The aim is to "bring together a lot of countries from around the world with the specific goal of looking at the Iranian regime through a more realistic lens" which would include "all of its destabilizing activities that aren't just a threat to the region but are a threat to the broader world," she said.

Nauert added that the coalition will not be "anti-Iran" because the US stands "firmly behind" the country's people, in contrast to the regime and its "bad actions."

She evoked a comparison with the US-led international coalition against the Islamic State group in Syria and Iraq.

Begun in 2014, that coalition now counts as members 75 countries or institutions and intervened militarily against the jihadists, although only a minority of coalition members have conducted most of that military action, which has left the extremists nearly defeated on that battlefield.

Nauert did not say whether the proposed coalition against Iran's regime would have a military component.

She said the State Department received on Monday about 200 foreign diplomats to explain to them President Donald Trump's decision to withdraw from the nuclear accord, and the next steps.

In a breakthrough that ended a 12-year standoff over Western fears that Iran was developing a nuclear bomb, the administration of former president Barack Obama and other major powers reached the accord with Iran in 2015.

It lifted punishing international sanctions in return for Iran's agreement to freeze its nuclear effort.

Withdrawing from the deal last week, Trump called for a new agreement with deeper restrictions on Iran's nuclear program as well as curbs on its ballistic missiles and its backing for militant groups across the Middle East.

Along with Iran the other signatories of the 2015 deal -- France, Britain, Germany, China and Russia -- strongly criticized the US withdrawal.

On Thursday the European Union said it will begin moves to block the effect of reimposed US sanctions on Iran as efforts to preserve the nuclear deal deepened a transatlantic rift.

Asked about the potential willingness of European nations to join the proposed new coalition, Nauert said many US allies "fully understand" and are "not turning a blind eye" to Iran's actions.