Donald Trump last night warned Iran he was 'loading up the ships with the best ammunition' in case today's crunch peace talks fail.

The US President's threatening rhetoric came shortly after Vice President JD Vance jetted off from Washington for in-person negotiations with Iranian officials in Pakistan.

As he was boarding Air Force Two, Mr Vance said he believed the discussions would prove 'positive'. 'If the Iranians are willing to negotiate in good faith, we're certainly willing to extend the open hand,' he said. 'If they're going to try to play us, then they're going to find that the negotiating team is not that receptive.

'We're going to try to have a positive negotiation. The President gave us some pretty clear guidelines, so we'll see.'

However, Mr Trump was less positive, telling the Iranians they had 'no cards' to play following the US's devastating bombing campaign.

He posted on his social media account: 'The Iranians don't seem to realise they have no cards, other than a short-term extortion of the world by using international waterways. The only reason they are alive today is to negotiate!'

The ceasefire announced by Mr Trump late on Tuesday has proven to be fragile, with various threats and conditions coming from both sides. One of the main sticking points in any long-term peace deal is likely to be the inclusion of Lebanon, which Israel has continued to pummel with missiles.

On Wednesday, Beirut said civilians were the main casualties in an operation that saw 100 targets bombed in ten minutes. At least 33 children were killed and 153 injured. Israeli prime minister Benjamin Netanyahu said he believed that Lebanon, home to terror group Hezbollah, was not included in the peace deal.

However, it emerged on Thursday that Mr Trump and White House envoy Steve Witkoff had ordered Mr Netanyahu – known as Bibi – to 'be more low-key' and 'calm down' on the strikes for fear of jeopardising negotiations.

'I spoke with Bibi and he's going to low-key it,' Mr Trump told NBC. 'I just think we have to be sort of a little more low-key.' 

Meanwhile, Israeli Defence Force chief Eyal Zamir said Israel remained 'in a state of war', adding: 'We are not in a ceasefire. We continue to fight here [in Lebanon], this is our primary combat zone. 

'In Iran, we are in a ceasefire, and we can return to fighting there at any moment, and in a very powerful way.'

The speaker of Iran's parliament Mohammad Bagher Ghalibaf said a full ceasefire in Lebanon and the release of Iran's blocked assets must happen 'before negotiations begin'. He said the two measures were agreed between the parties and 'have yet to be implemented'.

Mr Trump has said that he agreed a two-week, ten-point ceasefire plan with Iran, but the precise details are not known.

However, the full re-opening of the Strait of Hormuz, through which 20 per cent of the world's oil and gas passes, was 'non-negotiable', he said. 

While some tankers have crossed the strait since the ceasefire, Iran is understood to be charging tolls in bitcoin of $1 a barrel, potentially amounting to £2.2million per ship. 

Mr Trump had said they had 'better not' be doing this – but suggested that the US could enter a 'joint venture' with Iran and Oman to levy tolls.

In-person talks with Iran are due to start today in Islamabad, Pakistan, led by Mr Vance, Mr Witkoff and Jared Kushner, the President's son-in-law.

Prior to the talks, Khawaja Asif, Pakistan's defence minister, tweeted that Israel was 'a curse for humanity'. 'While peace talks are underway in Islamabad, genocide is being committed in Lebanon,' he wrote in the since-deleted message. 

'I hope and pray people who created this cancerous state on Palestinian land to get rid of European jews [sic] burn in hell.'

Mr Netanyahu described the tweet as 'outrageous', adding: 'This is not a statement that can be tolerated from any government, especially not from one that claims to be a neutral arbiter for peace.' 

Meanwhile, Hezbollah chief Naim Qassem called on the Lebanese government to stop giving 'free concessions' to Israel.

The two governments are due to begin negotiations in Washington next week.

'We will not accept a return to the previous situation, and we call on officials to stop offering free concessions,' Qassem said.