Jordan’s foreign minister, Ayman Safadi, has made a rare visit to Iran in a last-ditch effort to persuade it to hold back from attacking Israel in response to the assassination of the Hamas political leader, Ismail Haniyeh, in Tehran last week.

The western ally with a large Palestinian population is facing a tough balancing act as it faces domestic calls to break off relations with Tel Aviv and to stop protecting it after shooting down Iranian missiles aimed at Israel earlier this year.

The visit looks doomed to fail given that Iran insisted on Sunday that there was no room for compromise and that it would make a decisive response to the assassination.

In the previous Iranian attack on Israel in April, Jordan shot down some Iranian missiles flying over its airspace insisting it would not allow its country to become a battlefield for other conflicts. It also gave the French navy permission to deploy radars.

But the kingdom is also facing mass demonstrations in support of Gaza and is furious with the Israeli prime minister, Benjamin Natanyahu, for assassinating Haniyeh in what it has condemned as “an escalatory crime and flagrant violation of international law”. Israel has refused to officially comment on Haniyeh’s assassination, but its role is widely acknowledged.

More than half the Jordanian population is Palestinian or of Palestinian descent.

Iran insists the assassination has crossed too many red lines and is calling for a meeting of the Organisation of Islamic Cooperation (OIC), at which Tehran would put pressure on Arab Gulf states including Saudi Arabia and the United Arab Emirates to adopt sanctions against Israel.

Safadi’s visit to Iran is the first visit by a Jordanian foreign minister for two decades, and reflects the failure of a phone call between the two sides to find a diplomatic solution.

His condemnations of Israel’s treatment of Palestinians has been strikingly vivid in recent months. “The Israeli government acts in a way that reflects their racism, extremism and rejection of the right of the Palestinians to live like any other people on this Earth,” he said recently. But Jordan is hugely dependent on the US for its security, and will rejoin the April alliance to minimise the impact of any Iranian assault.

A lively debate is also under way in Tehran among former diplomats and politicians about how to respond in a way that does not play into Netanyahu’s hands. The final decision rests with the supreme leader, Ayatollah Ali Khamenei and the advice given by the Islamic Revolutionary Guards Corps (IRGC).

Most comment in Tehran assumes Netanyahu’s attack was designed to undermine the newly elected government of the reformist leader Masoud Pezeshkian, and its desire to explore better relations with the west. Israel vowed to kill all Hamas leaders after the 7 October attacks, and its intelligence services have a history of carrying out covert killings inside Iran.

Iran has also been interested in US media reports that Joe Biden upbraided Netanyahu in a phone call on Thursday for misleading him over his plans to assassinate Haniyeh, who was also the chief Hamas negotiator in ceasefire talks, and for setting increasingly impossible preconditions in the talks.

Reports from Israeli media were also widely picked up suggesting Netanyahu’s intelligence and defence chiefs told him they could not reach a ceasefire deal on the parameters he had set them.

But there is scepticism in Tehran that Biden’s frustrations with the Israeli leadership will lead to any effective pressure on Netanyahu to give his negotiators a new more flexible brief. Talks at the weekend made no progress, and the speaker of the Iranian parliament, Mohammad Qalibaf, called for a decisive Iranian response.

Pezeshkian is still in the process of forming his government, but has appointed Javad Zarif as his vice-president for strategy, a post that may give him more influence than when he was foreign minister. Zarif strongly favours greater contact with the west and helped complete the negotiations that led to the Iranian nuclear deal in 2015. He also has long experience of the forces inside Iran that will seek to undermine him.

The internal debate in Iran about the correct military response has also been coloured by the often bitter debate about whether Iran’s intelligence services have been penetrated by their Israeli counterpart, the Mossad, or instead have just been woefully incompetent.

The IRGC‘s official explanation is that Haniyeh was killed by a “short-range projectile” launched from outside his accommodation in northern Tehran.

The Israeli military spokesperson Daniel Hagari had earlier told journalists “there was no other Israeli aerial attack ... in all the Middle East” on the night the Hezbollah leader Fuad Shukr was killed in Lebanon.

The IRGC explanation differs from the claim that a bomb was placed in Haniyeh’s bedroom two months ago, and was then detonated when he came to Tehran for Pezeshkian’s inauguration. Either explanation requires a level of knowledge about Haniyeh’s precise sleeping arrangements in Tehran because only his apartment was targeted.

Tehran is awash with rumours of betrayal by the intelligence services, including denied reports that Hassan Karmi, the commander of Faraja special units, , had been arrested for espionage. Abolfazl Zahravand, a member of the Iranian parliament’s national security commission, said: “The Israelis have an influence network inside Tehran and Iran. Evil elements cooperate with them, who have defined themselves in the ‘Mossad network’.”

The accuracy of the conflicting and often bizarre “exclusive” explanations of the causes of Haniyeh’s death are all coloured by the desire of various intelligence agencies, western and Iranian, as well as some newspapers, to undermine their rivals.