As Egypt spearheads Arab opposition to President Trump’s “Mideast Riviera” plan for Gaza, concerns are growing in Israel over Cairo’s military power on its border. Will the two countries, which battled each other four times prior to signing an unprecedented peace treaty, return to war? 

Mideast social media is filled with documentation of an Egyptian tank buildup in the Sinai desert near the Israeli border. The Israeli ambassador to Washington, Yechiel Leiter, is warning that amassing “offensive weapons” in that area might be a violation of the 1977 treaty signed by the two countries. 

In back-room contacts with Israeli intelligence officials, their Egyptian counterparts are attempting to be reassuring. Yet, some at Jerusalem are asking: What enemy is Egypt preparing for as its military grows by leaps and bounds? “The Israelis are worried,” a Western diplomat at Cairo tells the Sun.

On October 7, 2023, the diplomat notes, Israel missed signs of danger because its elites believed public statements that indicated Hamas was not ready to attack. Since then, though, “they are paying less attention to intentions, and more to offensive capabilities,” he says. “What a potential enemy intends to do is unknown, but offensive capabilities can be observed.”

Speaking to the Conference of Presidents of Major Jewish Organizations three weeks ago, the new Israeli ambassador to America, Mr. Leiter, a confidante of Prime Minister Netanyahu, warned of Egypt’s build up. 

While the meeting was behind closed doors, the Conference over the weekend posted parts of his remarks on video. Cairo “is committing a grave violation of the peace agreement in Sinai,” he said. “Egypt is building bases intended only for offensive operations. For a long time, this issue has been silenced. Israel intends to raise the issue very soon, and very firmly.” 

For now Egypt plans no attack on Israel, an Egyptian commentator, Amr Adeeb,  who has close ties with President al-Sisi’s government, told his television audience Sunday evening. The Arab affairs analyst for Israel’s Kan news, Roi Kais, who aired the remarks on Monday, noted the implicit threat in the commentary. 

“At the moment,” Mr. Adeeb said, “and I ask you to note, ‘at the moment,’ that is at 10:15 p.m. — I mean now and under the current circumstances — we don’t intend to wage war on Israel.” 

At the moment? “It looks like Egypt is training and preparing for a confrontation with Israel,” a researcher , Ruth Landa, at an Israeli think tank, Misgav, told a Hebrew-language radio interviewer recently. “They are amassing troops in the Sinai. The military growth is real and requires an explanation.”

As part of the 1979 Israeli-Egyptian peace deal, America is providing military aid to Cairo that now stands at $1.4 billion a year. To justify that support, the Sisi government needs to plausibly explain to Washington why it needs such considerable military growth, Ms. Landa says. 

Cairo is battling Ethiopia over water resources, but that dispute requires no major firepower. The 1979 treaty limits the Egyptian military presence in the Sinai. Representatives of the two countries and America are charged with ensuring that condition. At times Jerusalem agrees with Cairo’s needs. As Egypt fought ISIS in the peninsula in the last decade, Israel did not oppose added military presence in the Sinai. 

Kan news is reporting that Mr. Netanyahu is personally charged with approving “each tank” that enters the Sinai. Violations, though, are normally dealt with in quiet talks between Jerusalem and Cairo. Yet, as Mr. Leiter’s comments perhaps indicate, in this case the backroom negotiations are hitting a snag. 

Egypt has long dreaded being responsible for the Palestinians in Gaza, which it had occupied until 1967. President Sadat refused Prime Minister Begin’s proposal to transfer the Strip to Egypt’s sovereignty as part of the peace treaty. After Israel withdrew settlements and all troops in 2005, Egypt beefed up its forces on the Gaza border. 

Since Hamas launched the war on October 7, 2023, Cairo stood fast against any suggestion that Palestinian civilians would shelter in its territory. Egypt was alarmed when Israeli troops seized the Philadelphi corridor on its border with Gaza. It built up fortifications on the Egyptian side of the border to prevent Gazans from getting in. 

Cairo now is attempting to unite an Arab response to Mr. Trump’s plan to move Gazans out as the Strip is rebuilt. Mr. Sisi is expected to visit Riyadh on Thursday to present to the Saudi crown prince, Mohamed bin-Salman, an alternative Gaza rehabilitation plan. 

As yet, though, Mr. Sisi is struggling to convince fellow Arabs: An Arab League summit he planned to convene February 27 has now been pushed to early March, Cairo announced Tuesday.