He told viewers that the US had only intervened in the war because 鈥渋t felt that if it did not intervene, the Zionist regime would be utterly destroyed鈥.
But he said, however, that the US 鈥渁chieved no gains from this war鈥.
鈥淭he Islamic Republic was victorious and, in retaliation, delivered a hand slap to America鈥檚 face,鈥 he said, in apparent reference to an Iranian missile attack on an American base in Qatar on Monday, which caused no casualties.
The 86-year-old Mr Khamenei hasn鈥檛 been seen in public since taking shelter in a secret location after the outbreak of the war June 13 when Israel attacked Iranian nuclear facilities and targeted top military commanders and scientists.
Following an American attack on June 22, which hit the nuclear sites with bunker-buster bombs, US President Donald Trump was able to help negotiate a ceasefire that came into effect on Tuesday.
In his appearance on Thursday, he sat in front of plain brown curtains to give his address, similar to his June 19 message.
It comes as Mr Trump earlier insisted that US strikes had delivered a crushing blow to Iran鈥檚 nuclear programme despite a preliminary American intelligence assessment suggesting that the assault inflicted only a marginal setback.
鈥淭his was a devastating attack, and it knocked them for a loop,鈥 Mr Trump said as his administration deployed a phalanx of top officials to defend his claims that Iran鈥檚 nuclear programme was 鈥渃ompletely and fully obliterated鈥.
US defence secretary Pete Hegseth said the leaked intelligence assessment, which said Iran suffered a delay of only a few months, was 鈥減reliminary鈥 and 鈥渓ow confidence鈥.
US secretary of state Marco Rubio said the officials who disclosed the findings are 鈥減rofessional stabbers鈥.
The White House pointed to a statement from the Israel Atomic Energy Commission that said Iran faced a setback of 鈥渕any years鈥.
Drawing reliable conclusions about the impact of the US strikes is difficult, making the issue a breeding ground for competing claims that could determine how American voters view Mr Trump鈥檚 risky decision to join Israel鈥檚 attacks on Iran.
Also at stake are Mr Trump鈥檚 next steps in the Middle East, where diplomatic efforts could be required to prevent Iran from rebuilding its nuclear program.
Iran maintains that its atomic ambitions are for peaceful purposes, while US and Israeli leaders have described the country鈥檚 nuclear programme as the precursor to obtaining a nuclear weapon.
One of the targets of the US attack was Fordo, where nuclear infrastructure is buried deep underground.
The Israeli commission said in a statement that the bombing 鈥渞endered the enrichment facility inoperable鈥.
The statement was distributed by the White House and the office of Israeli Prime Minister Benjamin Netanyahu.
The American strikes on Iran鈥檚 nuclear facilities, combined with Israeli strikes on other parts of Iran鈥檚 military nuclear programme, have 鈥渟et back Iran鈥檚 ability to develop nuclear weapons by many years鈥, the statement said.
In addition, Iranian Foreign Ministry spokesman Esmail Baghaei told Al Jazeera that there was significant damage from US bombers.
鈥淥ur nuclear installations have been badly damaged, that鈥檚 for sure,鈥 he said.