US President Donald Trump on Tuesday announced a two-week ceasefire in the six-week war, just hours before a deadline after which he had threatened to destroy Iran's civilisation.
The ceasefire has halted US and Israeli airstrikes on Iran. But it has not ended Iran's blockade of the Strait of Hormuz, which has caused the biggest-ever disruption to global energy supplies, or calmed a parallel war between Israel and Iran-backed Hezbollah in Lebanon.
Iran's parliamentary Speaker Mohammad Baqer Qalibaf said on X that Washington had previously agreed to unblock Iranian assets and to a ceasefire in Lebanon, and added that talks would not start until those pledges are fulfilled.
Iranian state media reported that Qalibaf arrived in Islamabad on Friday and the delegation includes senior political, military and economic officials, including Iran's foreign minister, defence council secretary, central bank governor and several members of parliament.
While there was no immediate comment from the White House on the Iranian demands, Trump said in a social media post that the only reason the Iranians were alive was to negotiate a deal.
"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!" he said.
US Vice President JD Vance, who will lead the US delegation, said he expected a positive outcome as he headed to Pakistan, but added: "If they're going to try to play us, then they're going to find the negotiating team is not that receptive."
Iran has been unable to obtain tens of billions of dollars of its assets in foreign banks, mainly from exports of oil and gas, due to US sanctions on its banking and energy sectors.
Israel and the US have said the campaign against militant group Hezbollah in Lebanon is not part of the agreed ceasefire.
Israel launched the biggest attack of the war hours after the ceasefire was announced, killing more than 350 people in surprise strikes on heavily populated areas, Lebanese authorities said.
Israeli strikes continued across southern Lebanon on Friday. One strike on a government building in the city of Nabatieh killed 13 members of Lebanon's state security forces, President Joseph Aoun said in a statement.
The hard line taken by Iran's leaders ahead of the negotiations followed a defiant message from its new Supreme Leader Ayatollah Mojtaba Khamenei on Thursday.
Khamenei, yet to be seen in public since taking over from his father, who was killed on the war's first day, said Iran would demand compensation for all wartime damage.
"We will certainly not leave unpunished the criminal aggressors who attacked our country," he said.
Iran still possesses missiles and drones capable of hitting its neighbours and a stockpile of more than 400kg of uranium enriched near the level needed to make a bomb.
Its clerical rulers, who faced a popular uprising just months ago, withstood the onslaught with no sign of organised opposition.
Tehran's agenda at the talks includes major new concessions, including the end of sanctions that crippled its economy for years, and acknowledgment of its authority over the strait, where it aims to collect transit fees and control access in what would amount to a huge shift in regional power.
Iran's ships were sailing through the strait unimpeded on Friday, while those of other countries remained hemmed inside.
with DPA
