Vice President Vance left Friday for Pakistan and the biggest challenge of his career: negotiating a deal with Iran to solve the nuclear dispute and end the war."This is a big deal for JD. He is going to the Super Bowl," one U.S. official told Axios.Why it matters: While the meeting itself is historic — the most high-level engagement between U.S. and Iranian officials since 1979 — the chances for success appear low. Both sides know the risk of failure is renewed war, but have clashing visions for peace."We still don't agree on what we are negotiating about," another U.S. official said.The countries have spent the lead-up to the talks accusing each other of ceasefire violations. The Iranians have been threatening not to show up at all. While Vance was in the air, Trump made a thinly veiled threat to kill Iran's leaders if they don't play ball.Driving the news: The talks are expected to start on Saturday in Islamabad, with the sides negotiating directly and Pakistani officials serving as mediators.Vance will be accompanied at the talks by Trump's envoys, Steve Witkoff and Jared Kushner. His delegation also includes officials from the National Security Council and departments of State and Defense."We are looking forward to the negotiation. I think it is going to be positive," Vance said before departing Andrews Air Force Base. He said Trump gave the negotiating team "pretty clear guidelines.""If the Iranians are willing to negotiate in good faith, we are willing to extend the open hand... if they try to play us they are going to find that the negotiating team is not that receptive," Vance said. The other side: Two hours after Vance left Washington, his counterpart in the negotiations reiterated his threat to boycott the talks if Iran's conditions aren't met."Two of the measures mutually agreed upon between the parties have yet to be implemented: a ceasefire in Lebanon and the release of Iran's blocked assets prior to the commencement of negotiations. These two matters must be fulfilled before negotiations begin," Speaker of Parliament Mohammad Bagher Ghalibaf wrote on X. It's not clear which blocked assets Ghalibaf was referring to. During the negotiations in February, the Trump administration considered unfreezing $6 billion held in a bank account in Qatar and allowing Iran to use it to buy food and medicine.Trump then published a post of his own: "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!"Behind the scenes: Vance asked Trump for a role in Iran diplomacy, two U.S. sources said. Another reason he came to lead the U.S. delegation is the bad blood between Trump's envoys and the Iranians after two previous sets of talks ended in war, according to the sources.Iranian officials have told the mediators they think Witkoff and Kushner deceived them, and that — given Vance's seniority and skepticism about going to war in the first place — having the VP involved could enable progress, the sources said."Vance asked for the ball and he got it. He can be responsible for getting the deal that will end the war," a U.S. official said. "Of course the vice president wanted to be involved in such an important moment, and when the president asked he enthusiastically agreed to lead the negotiations," a source close to Vance said.Yes, but: While sending Vance is a signal the U.S. is serious, some officials are concerned that sending such a high-level principal might be premature, as so little groundwork has been laid for the negotiations.The source close to Vance rejected that characterization and said Witkoff and Kushner had been negotiating with Iran for weeks"The Vice President, Secretary of State, Special Envoy, and Mr. Kushner have always been collaborating on these discussions about Iran, and the President is optimistic that a deal can be reached that can lead to lasting peace in the Middle East," White House spokesperson Anna Kelly said.The intrigue: While some skeptics of the war within the MAGA base see Vance as an ally, Trump has been on the attack against those voices and leaning toward hawkish figures like commentator Mark Levin who have praised his decision to go to war."The Tucker Carlson side of the party got shit on by Trump. That's not good news for JD," a source close to Trump said. Trump also made clear over the last 24 hours that he's frustrated by Iran's behavior — especially the refusal to open the Strait of Hormuz — and that the U.S. is replenishing ammo to resume the fighting if talks fail."In theory, Trump wants a deal, but he is also getting ready to resume the war. The way the Iranians behave pissed him off. They are sort of embarrassing the guy," the U.S. source said. What to watch: U.S.