Iran's supreme leader threw his support behind the elite Revolutionary Guards in a rare sermon on Friday after their belated admission that they had accidentally downed an airliner triggered days of street protests.
In his first Friday prayers sermon for eight years, Ayatollah Ali Khamenei also told worshippers chanting "Death to America" that the elite Guards could take their fight beyond Iran's borders after the US killing of a top Iranian commander.
US President Donald Trump hit back later on Twitter, writing that Khamenei should be careful what he says.
Khamenei's address came amid a deepening crisis for Iran as it grapples with unrest at home and rising pressure from abroad.
Tension has steadily ratcheted higher since 2018, when the United States withdrew from Tehran's nuclear pact with world powers and reimposed sanctions that have hammered the economy.
The standoff erupted into tit-for-tat military strikes this month, when Washington killed top commander Qassem Soleimani in a drone strike on Jan. 3 and Iran launched missile strikes at US targets in Iraq on Jan. 8.
In the tense aftermath, a Ukrainian airliner was shot down by mistake. But it took days for the Guards to admit this and protesters directed their rage at the elite force and the clerical system it was set up to defend.
"Our enemies ... were happy that they found an excuse to undermine the Guards, the armed forces and our system," Khamenei said in his sermon, heaping praise on the Guards for protecting Iran and renewing a call for U.S. troops to leave the region.
Khamenei said Soleimani's work of projecting Iran's military influence abroad would continue and said the Quds Force he commanded "protects oppressed nations across the region."
He said Quds Force soldiers were "fighters without borders."
The US State Department's special representative for Iran, Brian Hook, said in Washington that Iranian threats risked further isolating the country.
But Russia lent Iran some support over the airliner disaster, saying it had been shot down when Tehran was spooked by reports of advanced US stealth fighters in the area.
"I'd like to underline the edginess that always accompanies such situations," Foreign Minister Sergei Lavrov said.