How could Pakistan's involvement in U.S.-Iran talks affect peace and relations in the region?

Pakistan's top military commander, Field Marshal Asim Munir, landed in Tehran on Friday as part of an effort to reach a deal under which the U.S. and Iran would agree to end the war and launch negotiations for a broader agreement, a Pakistani security source told Axios. Why it matters: Munir has been the lead mediator between the U.S. and Iran since the war began. The fact that he's in Tehran after several days of lower-level talks could signal a final push by Pakistan to try to get a deal. The latest: Munir arrived in Tehran on Friday and was received by Iranian Interior Minister Eskandar Momeni, the Pakistani military said in a statement. A Qatari delegation also arrived in Tehran to support the mediation effort, Reuters first reported and a source familiar confirmed to Axios. Driving the news: The mediators are trying to finalize a letter of intent that includes an agreement to end the war and principles for another 30 days of negotiations on a broader deal that would also address Iran's nuclear program. Pakistan, Qatar, Saudi Arabia, Egypt and Turkey have all been involved in the mediation.It has remained unclear whether Iran would be willing to sign such a document at a time when some in Tehran appear to believe the leverage is on their side. What they're saying: "There's been some slight progress. I don't want to exaggerate it, but there's been a little bit of movement, and that's good," Secretary of State Marco Rubio said on Friday. He added that the fundamental demand is that "Iran can never have a nuclear weapon. It just cannot."Rubio said a deal would have to address Iran's stockpile of highly enriched uranium and enrichment policy going forward.He also said Iran must not be allowed to set up "tolls" in the Strait of Hormuz, after Iran reiterated its intention to establish such a system on Thursday. Go deeper: Trump bleeds votes in Congress to keep Iran war going This story was updated to note Munir's arrival in Tehran