"We're looking forward to the negotiation. I think it's going to be positive," Vance told reporters before leaving Washington DC.
"As the president of the United States said, if the Iranians are willing to negotiate in good faith, we're certainly willing to extend the open hand," Vance said.
"If they're going to try to play us, then they're going to find the negotiating team is not that receptive."
According to the White House, the US delegation led by Vance also includes special envoy Steve Witkoff and US President Donald Trump's son-in-law Jared Kushner.
Security sources in Pakistan have indicated that preliminary talks at expert level are planned.
A meeting of the chief negotiators is planned for Saturday.
The talks could therefore continue into Sunday if necessary.
The Strait of Hormuz remained closed and Israel launched new attacks on Lebanon on Friday, which the United States and Iran each flagged as violations of their ceasefire deal.
The two-day-old ceasefire has halted the campaign of US and Israeli air strikes on Iran.
But it has so far done nothing to end the blockade of the strait, which has caused the biggest-ever disruption to global energy supplies, or to calm a parallel war waged by Israel against Iran's Hezbollah allies in Lebanon.
Iran was doing a "very poor job" of letting oil through the strait, Trump said in a social media post.
He also warned Iran against trying to collect fees from ships crossing it: "That is not the agreement we have!"
Iran said ongoing Israeli attacks on Lebanon were a violation of the truce.
Israeli forces launched the biggest attack of the war hours after the ceasefire was announced, killing more than 250 Lebanese in surprise strikes on heavily populated areas.
Israeli strikes continued across southern Lebanon on Friday, with more than a dozen people reported killed in various towns.
One strike killed eight members of Lebanese state security forces, Lebanon's state media said.
In a shift on Thursday, Israel said it would open separate talks with the Lebanese government aimed at ending the war there and disarming Hezbollah.
A US State Department official confirmed the United States would host an Israeli-Lebanese meeting next week.
A Pakistani source said "everything is on track" for the US-Iran peace talks to start on Saturday as planned.
Speaking before the reports of the latest Israeli strikes on Lebanon, he said a reduction in violence there was positive.
"It has de-escalated. Good sign."
But Iran's parliament Speaker Mohammad Baqer Qalibaf said on Friday that two previously agreed measures, a ceasefire in Lebanon and the release of Iran's blocked assets, must be implemented before negotiations begin.
In a post on X on Friday, Qalibaf said the steps were part of commitments made between the parties and warned that talks should not start until they were fulfilled.
Advance teams from both countries were already in place in the five-star Serena hotel in central Islamabad where both delegations would stay for the duration of the talks.
There were no face-to-face meetings planned for Friday but Pakistan was relaying messages between them, the source said.
The centre of Islamabad was placed under complete lockdown for a hastily announced public holiday, with a security perimeter thrown up for a 3km "red zone" around the hotel.
with DPA
