Tehran, Iran - Iran's supreme leader Ayatollah Ali Khamenei said on Thursday that President Donald Trump's administration was "not worthy" of contact or cooperation with the Islamic republic.

"Such a government is not worthy of being approached or cooperated with by a government like the Islamic Republic," Khamenei said in a televised speech, rejecting rumors that Iran had sent messages to Washington as a "pure lie".

His remarks came on the occasion of a state-designated day celebrating the Basij forces, a paramilitary force under the Islamic Revolutionary Guard Corps.

Khamenei said the US and Israel had failed "to achieve any objectives" during the 12-day war between Israel and Iran in June.

That month, Israel launched an unprecedented bombing campaign against Iran, triggering a war that the US briefly joined with strikes on key Iranian nuclear facilities.

Israel's attack prompted an Iranian response of missile and drone strikes and derailed nuclear talks between Tehran and Washington that had begun in April.

A ceasefire between Iran and Israel has been in place since June 24.

During his speech, Khamenei praised Iran's "public unity" during the war, saying "even those who had differences with the system stood by it."

This unity, he said, "must be preserved and appreciated," he added.

Khamenei previously said Israel's attacks during the war had sought to weaken the Islamic Republic, sow "unrest and bring people into the streets to overthrow the system".

Since the war, Trump has repeatedly said the US strikes obliterated Iran's nuclear program, but the full extent of the damage remains unknown.

The Pentagon has said the strikes delayed Iran's nuclear program by between one and two years, contradicting an initial classified US intelligence report that, according to American media, found the setback was only a few months.

Khamenei has previously rebuffed Trump's claims that Iran's nuclear program had been destroyed, telling him to "keep dreaming."