International efforts to fight Islamic State, galvanised by the Paris attacks, are putting pressure on Arab states to do more, a year after they first joined Barack Obama’s coalition to “degrade and ultimately destroy” the jihadi group.

But rivalry with Iran, disagreements over Syria, sectarian hatred and domestic public opinion are all acting as a brake on deeper involvement. US-backed Kurdish forces, Iraqi Shia militias and the Lebanese Shia Hezbollah have all battled Isis, known as Daesh to Arabs. Finding Sunni Arab ground forces is proving difficult.

And growing signs that military action against Isis is now taking precedence over the future of Syria and hopes that Bashar al-Assad will be forced out mean that it may well be impossible, say analysts and commentators from the Middle East and abroad.

Saudi Arabia, the UAE, Jordan and Bahrain are all still listed by US Central Command as taking part in airstrikes against Isis, which is politically important to Washington as a demonstration that there are Arab partners in a vicious regional war with global repercussions.

Early propaganda flaunted the combat roles of a Saudi prince and a female Emirati pilot. And the results were positive during the Isis siege of Kobani, when Arab sorties provided Syrian Kurdish fighters with badly needed air support

But for months now there have been few or no Arab attacks. The Saudi-led war in Yemen launched in March – against Houthi rebels who the Saudis insist are backed by Iran – has diverted resources and underlined the priority being given to the Gulf’s unstable and impoverished backyard.

Operation Inherent Resolve, as the US-led anti-Isis campaign was clunkily named, has demonstrated how so many Middle Eastern problems are inherently unresolved, in the words of a recent study by the Rusi thinktank, and are hobbling collective efforts.

The fundamental issue is that Isis is an enemy of the enemies of many Arabs – Iran and Assad, whom Tehran has backed to the hilt since the Syrian crisis began in 2011. “So far the Saudis still fear Iran in the long term more than they fear Daesh,” says Sultan Sooud al-Qassemi, an Emirati writer.

Emile Hokayem, of the International Institute of Strategic Studies, argues: “Everyone says they are against Isis, but it is no one’s top priority. It is not yet the organising principle of politics in this region.”

Officially, Arab partners insist nothing has changed. French raids on the Isis “capital” of Raqqa were launched from bases in Jordan and the UAE, though those countries’ own air forces were not involved. No one has forgotten the terrible fate of the Jordanian pilot Muath al-Kasasbeh, burned alive in a cage by his gloating captors.

King Salman of Saudi Arabia urged the redoubling of efforts to “eradicate this dangerous scourge and rid the world of its evils”. Isis has mounted terror attacks on Shia centres inside the kingdom to foment sectarian tensions. Prince Turki al-Faisal, its former intelligence chief, refers contemptuously to “Fahesh” (rhymes with Daesh), meaning simply “abomination”.

Like the Saudis, the Qataris dismiss accusations they helped create Isis by recklessly financing and arming Islamist rebels in Syria in their zeal to see Assad go. Not everyone believes them. But no one doubts that they fear it now.

Anwar Gargash, the UAE minister of state for foreign affairs, pledged to respond to any US request for further assistance. “We have been at the forefront of the war against terrorism and we will continue to be,” he said. “What we clearly see is that nobody is immune.”

Egypt, the most populous country in the Arab world, is preoccupied with a local war on terror in Sinai – fighting the jihadis of Ansar Bayt al-Maqdis, who were probably responsible for bombing a Russian airliner flying from Sharm al-Sheikh to St Petersburg in apparent retaliation for Moscow’s backing for Assad.

Arab reticence about tackling Isis is not primarily about military might: the Saudis and Emiratis have powerful air forces bought at vast expense from western defence manufacturers, though both are now busy pounding Yemen, its rising human toll overshadowed by the larger conflict in the Levant.

“The Gulf states are pursuing contradictory policies,” suggests Abdullah Saleh Baabood, an Omani academic. “On the one hand there is this official undertaking to fight Daesh but at the same time they are involved in a struggle against what they consider to be the Shia/Persian domination of the region. Yes, they want to be seen to be helping their allies but they are deeply concerned about domestic views. They don’t want to be seen to be fighting Sunnis. It is a very difficult situation for them.”

Longstanding Arab suspicions of Iran have worsened markedly since July’s landmark nuclear deal with Tehran. Angry exchanges over the recent hajj disaster in Mecca have also heightened tensions with Riyadh.

“You can’t just say the Saudis are the problem,” argues Qassemi. “They are also part of the solution. It’s not black and white. There’s a lot of grey as well. Why should they stick their necks out to fight an enemy of their enemies, Assad and Iran? The ball is in the Iranians’ court to offer a gesture of goodwill to the Saudis. That could be pushing the Houthis to attend peace talks in Yemen with a serious position, or lower the level of hostile rhetoric on Bahrain.”

Ambivalence in Arab capitals also reflects fears of growing domestic sympathy for Daesh and al-Qaida, in the absence of any political reform in the bleak aftermath of the Arab spring, in monarchies and republics alike.

“We are seeing terrible polarisation that leaves no middle ground – across government, society and amongst intellectuals,” says Baabood. “There is no room for another opinion. It’s us versus them, Shia versus Sunnis and Persians against Arabs. The disease has not been tackled, Daesh is a symptom. We have to tackle the root cause.

“In private many people do defend Daesh – not necessarily their brutality, but they try to justify it in one way or the another. They say: ‘OK they’ve killed a few people, but look how many Syrians have been massacred by Assad or Shia militias or Palestinians by Israel or Iraqis by western intervention.’”

National interests everywhere take precedence over regional ones. Turkey insists it backs the fight against Isis but seems more concerned to contain its Kurdish enemies at home and across the borders in Iraq and Syria. Iran boasts of its commitment to fight “tafkiri” terror – its codename for Sunni extremists – while keeping Assad in power and maintaining its dominance in Baghdad.

“As long as the rift between Iran and the Saudis is so wide, they won’t join the same coalition,” says Joseph Bahout, a French-Lebanese scholar at the Carnegie Endowment in Washington. “The second impediment is the Assad question. Unless that is tackled, you won’t be able to mobilise Sunni forces – either Syrians or other Arabs.

“The only people who can undertake something serious against Isis – without putting western boots on the ground, which would really not be wise – are Syrians who are fighting to be free both of Isis and the regime. They won’t fight Isis in order to return to Assad’s dungeons.”

Abdelkhaleq Abdulla, a political scientist who teaches in Dubai, agrees: “The basic problem is this belief that Assad has to stay and that he is needed to defeat Isis. We think exactly the opposite. The longer he is there, the longer Isis will be there. There is no way on earth that Sunnis in the Gulf and elsewhere will join the fight. The Saudis have made that clear and we all follow them.”