Trump’s national security adviser launched a rhetorical shot across Iran’s bow on Wednesday, in a terse public statement that hinted at possible military action to come.

“As of today, we are officially putting Iran on notice,” said White House National Security adviser ret. Lt. Gen. Michael Flynn in response to Iran testing a medium-range ballistic missile Sunday.

What would the U.S. do if Iran fired another missile? Neither Flynn, nor other administration officials would say, though they said they were reviewing a range of options.

Yet even as they insisted that the missile test was a violating of UN resolutions, those officials were careful to say this had nothing to do with the joint nuclear agreement signed by Iran and the world’s major powers – signaling that President Donald Trump is trying to thread the needle between maintaining the nuclear pact and signaling to Iran that other bad behavior won’t be tolerated.

Flynn, for his part, said the previous White House let Iran go too far, unchecked. “The Obama administration failed to respond adequately to Tehran’s malign actions, including weapons transfers, support for terrorism, and other violations of international norms,” he said. “The Trump administration condemns such actions by Iran that undermine security, prosperity, and stability throughout and beyond the Middle East and place American lives at risk.”

Trump administration officials explained that Wednesday’s warning is intended to let Iran know that the U.S. is aware of what they are doing—from backing Houthi rebels in Yemen to the latest ballistic missile launch—and is considering a number of unspecified actions to check that behavior.

The officials said Iran’s Sunday launch of the “Khoramshar” medium-range missile was “highly provocative and in defiance of the provisions of UN Security Council Resolution 2231,” which calls on Iran not to undertake any activity related to ballistic missiles designed to be capable of delivering a nuclear weapon. (Tehran, it should be noted, does not share in that assessment.)

“The missile was inherently capable of delivering a nuclear device,” said one of the officials, who added that the administration would be exploring what intelligence the U.S. could share with the UN Security Council, as the White House presses for enforcement of the resolution. The officials spoke on condition of anonymity as a condition of briefing the press corps.

The officials said the U.S. was also reviewing options for the next time Iran committed a perceived infraction included economic measures, but would not be drawn on whether there might be a U.S. military response.

Still, the smell of gunpowder hangs in the air, and the Trump challenge will be red meat to Iranian hard liners who criticized the deal, and just possibly a kick in the gut for moderate Iranian politicians who staked careers on a nuclear deal yielding tangible economic benefits for their constituents.

Those economic benefits have been slow to materialize, despite tens of millions of dollars flooding back into Iran with many sanctions lifted, plus the return of $400 million from the U.S. to Iran as a down payment on $1.7 billion settlement for a weapons sale Washington, D.C. refused to honor after the 1979 fall of Shah Mohammad Reza Pahlavi.

The Obama administration had hoped to empower ordinary people – and ordinary Iranian politicians – with the influx of cash, to compete with the political power and influence of Iran’s deep state military and intelligence apparatus, which uses sanctions and their monopoly on major Iranian industries to fund a network of insurgencies and rebel groups to extend Iranian influence throughout the Middle East.

Some observers see a great deal of danger if the new administration strays from that path. "If General Flynn has his way, Iran will resume it former position at the heart is the terrorism problem set, right after ISIS,” said former CIA officer Scott Modell, of The Rapidan Group. “Flynn's criticism of Obama's overly conciliatory posture toward Iran, along with his view that the challenge of his lifetime is defeating radical Islamism, raises the odds of U.S.-Iran escalation,” he said in an email.

Yet today’s tough words could also be seen as a fulfillment of a Trump campaign promise. Trump pledged repeatedly to renegotiate the Joint Comprehensive Plan of Action, the so-called “Iran Deal,” which he called a lousy one, and to get tougher on Tehran.

This may prove awkward as the White House works to rebuild a relationship with Moscow in hopes of settling the conflict in Syria and working jointly to defeat the so-called Islamic State. Russia and Iran have grown increasingly close, with Russia acting as the go-between to help broker the nuclear deal, and Russia and Iran working together to prop up the Bashar Assad regime in Syria. Either the White House is forcing Russia to choose between allies—or offering it a chance to use its influence to clip Iran’s ambitions.

On Capitol Hill, the stern talking points aimed at Iran are proving succor to Republicans—who were almost universally critical of the Obama administration’s rapprochement with Tehran—and producing eye-rolls among Democrats, who were generally more supportive.

"I am very impressed with their seriousness about pushing back against Iran violations on the nuclear deal,” said Sen. Bob Corker, Republican chairman of the Senate Foreign Relations Committee, after meeting with retired Lt. Gen. Flynn Wednesday. "I'm very enthused about where they are on this issue,” he added, in comments to The Daily Beast.

Even Republicans who are typically skeptical of Trump have lauded the development.

“‘On notice’ means that if they continue what is obviously breaking the Iran agreement, appropriate actions will be taken,” Sen. John McCain, chairman of the Senate Armed Services Committee, told The Daily Beast. “It’s important to say to the Iranians that we know you have violated the treaty, and you’re on notice now… that's exactly the way to treat them.”

But to Democrats, putting Iran ‘on notice’ is a senseless escalation in rhetoric—especially since Flynn offered no detailed plan on how to act in reality. “Is it possible to be quoted sighing?” said one senior congressional staffer of the announcement, insisting on anonymity.

“I don’t know why the president is intent upon scaring everybody in America without giving us more details,” said Sen. Claire McCaskill, the top Democrat on the Homeland Security Committee.