Secretary of State Marco Rubio said the US military would step up its military attacks against Iran, a stark warning after two days of strikes across the country that the Trump administration says took out its leadership and crippled its ballistic-missile program.

“I’m not going to give away the details of our tactical efforts, but the hardest hits are yet to come from the US military,” Rubio told reporters on Capitol Hill. “The next phase will be even more punishing on Iran than it is right now.”

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Rubio was on the Hill to brief members of Congress on President Donald Trump’s campaign along with Israel to target Iran. He offered more clarity on the US objectives, saying the focus was to destroy the country’s Navy and attack drones, as well as its ballistic missile program, which it was using as a shield to fuel its nuclear ambitions.

Iran has long insisted that it didn’t want to build a nuclear bomb. While its ballistic missiles are capable of hitting US forces in the region as well as American allies, it didn’t have the capability to target the US directly.

Rubio denied regime change is the goal, even though the US-Israeli strikes have taken out Supreme Leader Ayatollah Ali Khamenei and dozens of other top leaders. He said there were currently no diplomatic exchanges happening with Iran.

“While we would love to see a new regime, the bottom line is — no matter who governs that country a year from now, they’re not going to have these ballistic missiles and they’re not going to have these drones to threaten us,” Rubio said.

Rubio didn’t rule out deploying ground troops but said the US wasn’t currently postured for a ground invasion and played down the possibility of that happening anytime soon.