Iran is ready to strike the US and Israel if they give it any reason to do so, the new head of the Islamic Revolutionary Guard Corps said in a televised speech on Thursday.
The regime is marking the 40th day since the death of top commander Qassem Suleimani.
"If you make the slightest error, we will hit both of you," Maj Gen Hossein Salami said at the ceremony saying:
Iranian state TV also aired an interview with Hezbollah leader Hassan Nasrallah, in which he said he had a close relationship with Suleimani.
Mr Nasrallah spoke of highlighting the role Suleimani played in helping to build up Hezbollah's rocket arsenal, and his own role in military operations during the group's war with Israel in 2006.
Suleimani, who was head of the Quds Force, the Guard's foreign operations branch, was killed by a US drone in Baghdad on January 3 along with Iraqi militia commander Abu Mahdi Al Muhandis.
Suleimani also played an important role in Iraq's battle against ISIS, Mr Nasrallah said.
He said the commander had asked for Hezbollah commanders to work with Iraqi security forces in battling the militant group when it stormed across large areas of Iraq in 2014.
Quds Force chief, Brig Gen Esmail Ghaani, read out Suleimani's will at a ceremony in Tehran.
In it he urged Iranians to support Iran's supreme leader Ayatollah Ali Khamenei and said political factions should put aside their differences.
Mr Khamenei said last week that Iran would support Palestinian armed groups as much as it could and urged Palestinians to confront a US plan for Israeli-Palestinian peace.
US President Donald Trump announced a plan that would set up a Palestinian state with strict conditions but allow Israel to take over long-contested Jewish settlements in the occupied West Bank.
Palestinian leaders reject it.
