Israel and Lebanon extended a shaky ceasefire by three weeks, President Donald Trump said Thursday, as the United States remained at a standstill in negotiations with Iran to end the Middle East war, reports AFP.

Trump announced the truce extension as he met with ambassadors of the two countries and despite recent Israeli strikes in Lebanon and fresh rocket fire from Iran-backed Hezbollah, which was not part of the talks in Washington.

"I think there`s a very good chance of having peace. I think it should be an easy one," Trump told reporters on Thursday. The initial truce had been set to expire on Sunday.

Still, the US president said earlier he was in no rush to end the war with Iran, adding that "the clock is ticking" for the Islamic republic as a third American aircraft carrier arrived in the Middle East.

Iranian media reported blasts over the capital Tehran, a first since the ceasefire in the Middle East war came into effect two weeks ago.

It was not clear what caused the explosions, though an Israeli security source told AFP that their country was not currently striking Iran.

Prospective peace talks in Pakistan were hanging in the balance, meanwhile, with no sign of a return to diplomacy to end a standoff in the Strait of Hormuz.

Since the ceasefire, the United States and Iran have shifted their focus to the Strait of Hormuz, a waterway through which a fifth of the world`s oil and liquefied natural gas exports ordinarily flow. Iran has effectively closed it in retaliation for the war.

"I have all the time in the World, but Iran doesn`t -- The clock is ticking!" Trump said on social media.

Trump, who on Thursday ruled out the use of a nuclear weapon against Iran, had earlier ordered the US Navy to destroy any Iranian boat caught laying mines in Hormuz.

- `Shoot and kill` -

The USS George H.W. Bush aircraft carrier has arrived in the Middle East, the US military said Thursday, bringing the number of the massive American warships operating in the region to three.

A second carrier was operating in the Red Sea on Thursday, while a third is also in the region, according to social media posts by US Central Command (CENTCOM).

Iran`s state news agency IRNA said the "sound of air defence firing" was heard in western Tehran, while the Mehr news agency reported that air defence systems were activated in several parts of the capital to counter "hostile targets".

Earlier, US forces boarded a vessel in the Indian Ocean that was transporting oil from Iran and a senior Iranian official said Tehran had banked its first proceeds from the tolls it exacts on shipping through the strait.

Trump had said he "ordered the United States Navy to shoot and kill any boat, small boats though they may be... that is putting mines in the waters of the Strait of Hormuz".

Israel`s Defence Minister Israel Katz meanwhile said "we are awaiting a green light from the United States -- first and foremost to complete the elimination of the Khamenei dynasty... and additionally to return Iran to the Dark Age and the Stone Age".

Iran has vowed it would keep the strait closed to all but a trickle of approved vessels for as long as the US Navy blockades its ports, brushing off demands from Trump to both reopen Hormuz and surrender its enriched uranium.

The US has imposed its own blockade of Iranian ports, and on Thursday the Pentagon announced that US forces had "carried out a maritime interdiction and right-of-visit boarding of the sanctioned stateless vessel M/T Majestic X transporting oil from Iran, in the Indian Ocean".