The visit comes as Pakistan steps up efforts to mediate between Washington and Tehran.Pakistan Army chief Field Marshal Asim Munir will travel to Tehran on Monday for talks with Iranian leaders as Islamabad seeks to revive stalled efforts to bring the United States and Iran back to the negotiating table.Iran's foreign ministry announced the visit on Sunday, saying Munir will discuss bilateral ties and regional issues during his stay. He will be accompanied by a delegation that is expected to hold high-level discussions with the Iranian leadership.The visit comes as Pakistan steps up efforts to mediate between Washington and Tehran after an agreement intended to create a 60-day window for high-level peace talks fell apart last month.Pakistan's mediation effortsPakistan had signed the interim peace agreement as a guarantor. However, the arrangement broke down as tensions in West Asia intensified and the US and Iran resumed military strikes.Pakistan has since been trying to restart the diplomatic process. Interior minister Mohsin Naqvi travelled to Tehran earlier this month, where he met Iranian President Masoud Pezeshkian and Foreign Minister Abbas Araghchi.Iranian foreign ministry spokesperson Esmaeil Baghaei said on Sunday that Munir's visit would focus on strengthening cooperation between the two countries and supporting efforts to promote peace and security in the region.Pakistan has not yet officially commented on the army chief's planned visit.Why the talks broke downThe stalled process followed a memorandum of understanding signed by the US and Iran in June. The agreement was intended to provide a 60-day period for high-level negotiations aimed at restoring peace in West Asia.However, the talks collapsed after tensions between Washington and Tehran escalated again in mid-July. Pakistan's subsequent attempts to bring the two sides back to negotiations have so far failed to produce a breakthrough.A major obstacle is the Strait of Hormuz, a key global shipping route that has been disrupted by the conflict. The war began on February 28 after the US and Israel launched joint attacks on Iran, prompting retaliatory strikes from Tehran. Under normal circumstances, around one-fifth of the world's energy supplies passes through the Gulf chokepoint.Iran warns against economic pressureIranian President Masoud Pezeshkian on Sunday defended the June agreement as the best way for Tehran to move beyond what he described as a situation of “neither war nor peace”.At the same time, Mohsen Rezaei, the hard-line new head of Iran's Supreme National Security Council, warned neighbouring countries against joining a fresh US effort to put pressure on Iran's economy.US President Donald Trump had warned on August 20 that Washington would launch what he called the “most crushing economic operation” against Iran if Tehran failed to reach a deal.