ISLAMABAD, April 11 (Reuters) - Senior US and Iranian leaders were in the Pakistani capital Islamabad on Saturday for negotiations to end their six-week-old war, although Tehran threw the talks into doubt by saying they could not begin without commitments on Lebanon and sanctions.

The US delegation, led by ​Vice President JD Vance and including President Donald Trump’s special envoy Steve Witkoff and son-in-law Jared Kushner, landed in two US Air Force planes at an air base in Islamabad on Saturday morning, where ‌they were received by Pakistan’s army chief, Field Marshal Asim Munir, and Foreign Minister Ishaq Dar.

The Iranian delegation, led by parliamentary Speaker Mohammad Baqer Qalibaf and Foreign Minister Abbas Araqchi, arrived on Friday.

These will be the highest-level US-Iran talks since the Islamic Revolution of 1979. If the two sides hold face-to-face negotiations as expected, they would be first direct talks since 2015, when they reached a deal on Iran’s nuclear programme.

Trump scrapped the nuclear deal in 2018 during his first term in office. That year, Iran’s then-Supreme Leader Ayatollah Ali Khamenei - who was killed at the start ​of the war six weeks ago - banned further direct talks between US and Iranian officials.

Iran has ‘no cards’, Trum says

Qalibaf said on X that Washington had previously agreed to unblock Iranian assets and to a ceasefire in Lebanon, ​where Israeli attacks on Iran-backed Hezbollah militants have killed nearly 2,000 people since the start of the fighting in March. He said talks would not start until those pledges were ⁠fulfilled.

Israel and the US have said the Lebanon campaign is not part of the Iran-US ceasefire.

Iran’s state broadcaster said the Iranian delegation would meet Pakistani Prime Minister Shehbaz Sharif around noon (0700 GMT) to determine the timing and manner of “possible negotiations”.

Qalibaf said ​Iran was ready to reach a deal if Washington offered what he described as a genuine agreement and granted Iran its rights, Iranian state media reported.

The White House did not immediately comment on the Iranian demands, but Trump posted on social media ​that the only reason the Iranians were alive was to negotiate a deal.

“The Iranians don’t seem to realize 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.

Vance, speaking as he headed to Pakistan, said he expected a positive outcome but added: “If they’re going to try to play us, then they’re going to find the negotiating team is not that receptive.”

Preliminary discussions have been separately held by Pakistani officials with advance teams from both sides, sources ​in Islamabad said.

Iran’s semi-official Tasnim news agency said these included 70 members from Tehran, including technical specialists in economic, security and political fields as well as media personnel and support staff. About 100 members of an advance US team were in the ​city, a Pakistani government source said.

Pakistan’s Dar said he hoped the US and Iran would engage in constructive talks to reach a “lasting and durable solution to the conflict”, according to a statement from Pakistan’s foreign ministry.

A Pakistani source said it was too early to say ‌whether talks would ⁠end on Saturday, adding there was no time limit for negotiations.

Islamabad was under an unprecedented lockdown ahead of the talks with thousands of paramilitary personnel and army troops on the streets.

Trump announced a two-week ceasefire in the war on Tuesday, which 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 the parallel war between Israel and Hezbollah in Lebanon.

Fighting continues in Lebanon

Israeli and Lebanese officials will hold talks in Washington on Tuesday, both sides said, amid conflicting accounts on what those talks would cover.

Lebanon’s presidency said officials from the two countries had spoken by phone on Friday and agreed to discuss announcing a ceasefire and ​setting a start date for bilateral talks under US mediation. ​But Israel’s embassy in Washington said the talks would ⁠constitute the start of “formal peace negotiations” and that Israel had refused to discuss a ceasefire with Hezbollah.

Tehran’s agenda at the Islamabad talks also includes demands for major new concessions, including the end of sanctions that crippled its economy for years, and acknowledgment of its authority over the Strait of Hormuz, 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.

Disruption to energy supplies has fed inflation ​and slowed the global economy, with ⁠an impact expected to last for months even if negotiators succeed in reopening the strait.

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 and said to be suffering from severe facial and leg injuries sustained in the attack that killed his father, said Iran would demand compensation for all wartime damage. “We will certainly not leave unpunished the criminal aggressors who attacked our country,” he said.

Although Trump has ⁠declared victory and ​degraded Iran’s military capabilities, the war has not achieved many of the aims he set out at the start: to deprive Iran of the ability ​to strike its neighbours, dismantle its nuclear programme and make it easier for its people to overthrow their government.

Iran still possesses missiles and drones capable of hitting its neighbours and a stockpile of more than 400 kg (900 pounds) of uranium enriched near the level needed to make a bomb. Its clerical ​rulers, who faced a popular uprising just months ago, withstood the war with no sign of organised opposition.