U.S. President Donald Trump’s national security team has over the past months conducted a series of meetings to discuss strikes against Iran.

As part of the talks, Trump’s National Security Council, led by John Bolton, asked the Pentagon to provide the White House with military options to strike Iran. The request, which hasn’t been previously reported, generated concern at the Pentagon and State Department, current and former U.S. officials say, according to the Wall Street Journal.

“It definitely rattled people,” said one former senior U.S. administration official. “People were shocked. It was mind-boggling how cavalier they were about hitting Iran.”

The Pentagon complied with the National Security Council’s request to develop options for striking Iran, the officials said. But it isn’t clear if the proposals were provided to the White House, whether Mr. Trump knew of the request or whether serious plans for a U.S. strike against Iran took shape at that time.

Garrett Marquis, a spokesman for the National Security Council, said the body “coordinates policy and provides the president with options to anticipate and respond to a variety of threats.”

“We continue to review the status of our personnel following attempted attacks on our embassy in Baghdad and our Basra consulate, and we will consider a full range of options to preserve their safety and our interests,” he said.

Bolton’s request reflects the administration’s more confrontational approach toward Tehran, one that he has pushed since taking up the post last April.

As national security adviser, Bolton is charged with providing a range of diplomatic, military and economic advice to the president.

Former U.S. officials said it was unnerving that the National Security Council asked for far-reaching military options to strike Iran in response to attacks that caused little damage and no injuries.

Last year, Defense Secretary Jim Mattis argued against strikes that might hit Russian and Iranian forces when Trump and his national security team were looking at ways to punish Syrian President Bashar al-Assad for an alleged chemical-weapons attack, according to people familiar with the debate. Mattis, who resigned last month amid a dispute with Mr. Trump over the president’s national security decisions, pushed for a more modest response that Trump eventually embraced.

In talks with other administration officials, Bolton has made it clear that he personally supports regime change in Iran, a position he aggressively championed before joining the Trump administration, according to people familiar with the discussions.

As a think-tank scholar and Fox News commentator, Bolton repeatedly urged the U.S. to attack Iran, including in a 2015 New York Times op-ed titled, “To stop Iran’s bomb, bomb Iran.”

After taking the White House post, Bolton joined forces with Secretary of State Mike Pompeo to develop a more aggressive policy aimed at weakening the government in Tehran. Bolton has said that his job is to implement the president’s agenda, which doesn’t include regime change in Tehran. The State Department declined to comment.

Bolton worked last year to quickly pull the U.S. out of former President Barack Obama’s nuclear deal with the country and to tighten economic sanctions on Tehran, moves eagerly sought by Trump. In a September speech, Bolton warned Tehran that there would be “hell to pay” if Iran threatened America or its allies.