The death of an Egyptian soldier in an exchange of fire near the Rafah crossing has added to tensions that have undermined Egypt's relationship with Israel since the start of the war in the Gaza Strip.
How deep are the ties?
After fighting wars with Israel in 1948, 1956, 1967 and 1973, Egypt became the first Arab country to sign a peace treaty and establish relations with Israel in 1979.
The treaty led to what has often been termed a "cold peace", under which economic, cultural and popular ties remained limited and marked by distrust. However, energy and security cooperation has been extensive and has intensified under President Abdel Fattah al-Sisi. Egypt began importing Israeli gas in 2020 and has hosted the East Mediterranean Gas Forum, of which Israel is a member.
The two countries also upheld a blockade on Gaza from 2007 when the territory came under the rule of Hamas, an offshoot of the Islamist Muslim Brotherhood movement that is outlawed in Egypt.
What caused recent tensions?
Egypt has been alarmed by Israel's military offensive in Gaza and the possibility that it could cause the mass displacement of Palestinians into Egypt's Sinai Peninsula - an idea floated by some Israeli politicians but strongly opposed by Arab states.
Egyptian officials and state-linked media have used increasingly blunt language to criticise the Israeli campaign, launched in response to an attack by Hamas on Oct 7.
Egypt has warned in particular against a large-scale military operation close to the Egyptian border in Rafah, where many of Gaza's residents had taken shelter from violence elsewhere in the enclave. When Israel stepped up operations around Rafah in early May and took control of the Gazan side of the Rafah crossing, humanitarian aid deliveries were halted, with Israel and Egypt blaming one another. Egypt says Palestinian management of the crossing must be restored.
Israel has angered Egypt by suggesting that Hamas has used tunnels running under the border into Sinai to smuggle arms. At the International Court of Justice this month, an Israeli delegate said about 50 such tunnels had been identified in Rafah.
Egypt says it destroyed tunnel networks leading to Gaza years ago and created a buffer zone and border fortifications that prevent smuggling.
What's at stake?
Most immediately, humanitarian aid flows into Gaza, where parts of the population face extreme hunger, and a critical lack of healthcare.
Though some aid has been sent through alternative routes including a US-built pier, most international aid has arrived in Sinai and was being routed through Rafah. Late last week, Sisi and US President Joe Biden agreed to restart aid through Israel's nearby Kerem Shalom crossing. Deliveries have resumed along this route but it is unclear how much they can be scaled up.
Egypt has also been at the centre of negotiations between Israel and Hamas aimed at agreeing a phased truce and releases of Israeli hostages held in Gaza as well as Palestinian prisoners held by Israel. The talks stalled as Israel moved into Rafah. Egypt threatened to withdraw from its mediation role after CNN cited anonymous sources suggesting Egyptian intelligence was responsible for scuttling a deal. Egyptian sources later said Egypt remained committed to negotiations. Ultimately, regional stability could be threatened if the relationship between Egypt and Israel frays. But while Egypt has warned that its peace treaty with Israel could be undermined by events in Gaza and has said it would join South Africa's case against Israel at the ICJ, it has not followed Jordan in withdrawing its ambassador to Israel or taken other formal steps.
Why would Egypt and Israel protect ties?
Both countries have an interest in keeping channels open as they try to manage the fallout from the war in Gaza as well as domestic and international pressures. For Egypt, the peace treaty has been a cornerstone of foreign policy for decades, generating $1.3 billion in annual military aid from the United States. Israel aims to build its ties with the Arab world rather than see them shrink. The two countries will also be central to post-war plans for Gaza and will have to come to an arrangement for managing security along the Egypt-Gaza border, including the Rafah crossing and a buffer zone known as the Philadelphi corridor.