Egypt, after months of measured condemnation of Israel over the Gaza war, has hardened its tone and formally supported an international case accusing its neighbour of genocide.
Cairo and its state-aligned media have stepped up scathing criticism of Israel over the conflict raging next door, reflecting public anger in the world's most populous Arab nation.
The two countries have also traded blame over the closure of Gaza's Rafah border crossing with Egypt, a crucial lifeline for aid trucks, since Israeli forces and tanks captured the Gaza side last week.
But despite the war of words, analysts don't expect a threat to the 1979 peace treaty between Israel and Egypt, both US allies and recipients of billions in American aid.
Since the worst ever Gaza war broke out with the Hamas attack of October 7, Egypt under President Abdel Fattah al-Sisi has walked a diplomatic tightrope.
While condemning Israel and warning it against pushing Palestinian refugees across the border, it has also mediated in truce talks, kept its ambassador in Israel, and long helped deliver aid through Rafah.
But its patience was been strained further as Israeli Prime Minister Benjamin Netanyahu has vowed a full ground invasion of Rafah city in southern Gaza, where about 1.5 million Palestinians have been pushed against the Egyptian border.
Cairo "was put in a position it didn't want to be in, where it had to react", said Cairo University political science professor Mustapha Kamel al-Sayyid.
Last Sunday, Egypt announced it would intervene in support of South Africa's case against Israel at the International Court of Justice in The Hague, without however announcing details.
Sayyid said the move signalled a "major shift", with Egypt "moving from criticising Israeli policies to joining in trying to prove it is committing a genocide".
- 'Backed into corner' -
Since Israeli forces seized the Gaza side of the Rafah crossing, Egypt has refused to coordinate aid deliveries through the Gaza border point.
When Israel's Foreign Minister Israel Katz said he hoped to "persuade Egypt" to reopen the crossing, his Egyptian counterpart Sameh Shoukry shot back that Israel was "distorting the facts and disavowing its responsibility" for Gaza's humanitarian crisis.
On Wednesday, Netanyahu again blamed Egypt and said Israel would want the Rafah crossing open "yesterday, if we could".
Ahmed Aboudouh, associate fellow at Chatham House, wrote this week that any agreements with Egypt on aid coordination had been bound to "crash under the weight of Israeli control of the crossing".
Emad Gad of Egypt's state-run Al-Ahram Center for Political and Strategic Studies said Israel had "embarrassed" key mediators Egypt and Qatar by going into Rafah, especially after Hamas had said it agreed to a truce proposal.
In response, he said, "Egypt is taking calculated steps" -- a view shared by other analysts, although many argued these are largely aimed at Egypt's domestic audience.
Aboudouh said joining the ICJ case remains a "largely symbolic" move, albeit one that "still reveals a deep sense in Egypt that it is backed into a corner and has to push back".
Nonetheless, he predicted that Cairo won't go so far as "to suspend the peace treaty", an option "everyone knows is not on the table".
- 'Cold peace' -
Egypt became the first Arab country to recognise Israel with the 1979 Camp David accords, and their relationship since has often been labelled a "cold peace".
The accords also demilitarised the Sinai Peninsula and limited the arms allowed on both sides of the border.
Sayyid said that Israel, by "putting tanks and armoured vehicles near the border", has already committed "a flagrant violation of the peace treaty".
Shoukry, when asked about the issue, called the treaty "a strategic choice" and said "violations are tackled within a technical, military framework under set mechanisms".
The language was in line with decades of careful security coordination, which has also allowed Egypt to move more forces into the Sinai to fight an Islamist insurgency over the past decade.
And with the neighbours' long history of quietly dealing with disagreements, Aboudouh said Egypt is likely to stick to its "risk-averse foreign policy".
Sayyid said Egyptian officials even seemed to "hesitate to respond" to Israel's Rafah operation, but said Cairo had "realised a limited response would not satisfy Egyptian public opinion".
Already, online footage showing Israeli flags on an armoured vehicle just across the Gaza border has stirred widespread anger in Egypt.
Aboudouh warned that the sight of "Egyptian aid being inspected by Israeli soldiers would be a nightmare for Egyptian officials, who would face unruly public anger".
Protests are banned in Egypt, but activist voices have called for stronger support for Palestinians in Gaza, where the war has claimed more than 35,000 lives.
State-aligned media has taken a harder line against Israel in what Sayyid called a "/media escalation". But Aboudouh wrote that even this should be "primarily understood as domestic (and pan-Arab) messaging".