CAIRO (AP) — Israel’s call Friday for half of the Gaza Strip’s population to evacuate south is hiking Egypt’s fears of a massive influx of refugees across the heavily fortified border into its territory.

Since Hamas’ bloody attack on Israel sparked a massive retaliation in Gaza, Egypt’s leadership has frantically tried to negotiate the entry of humanitarian aid through its crossing into the Palestinian territory — partially in hopes of averting an exodus into Egypt’s Sinai Peninsula. Officials say its efforts have received no response from Israel.

U.S. Secretary of State Antony Blinken was expected to visit Cairo over the weekend and Egyptian officials are expected to discuss the entry of aid with him.

Israel sealed off the Gaza Strip, stopping all entry of food, water, medicine and fuel to its 2.3 million people, while bombardment has leveled swaths of its cities. That has left Egypt’s Rafah crossing as the sole access. But repeated Israeli airstrikes at the Palestinian side of the crossing have forced it to stop operating, Egypt’s Foreign Ministry said, leaving trucks of aid stopped on the Egyptian side.

Egyptian President Abdel Fattah el-Sissi called for access through Rafah in a speech Thursday. He also pushed back against letting in large numbers of Palestinians.

“The threat there is significant because it means the liquidation of this (Palestinian) cause,” el-Sissi said at a military college graduation ceremony in Cairo. “It’s important for its people to stay steadfast and exist on its land.” He also pointed out that Egypt already hosts some 9 million refugees. That population swelled this year as 300,000 Sudanese fled their country’s war into Egypt, already facing economic crisis.

Khaled Gendy, a senior fellow at the Middle East Institute, said Egypt’s primary concern is that hundreds of thousands of refugees will become a permanent reality. “What sort of guarantees are there going to be for their return?” he said.

Palestinians and Arab nations are marked by the experience of the 1948 war surrounding Israel’s creation when Palestinians were expelled or fled to neighboring countries and have not been allowed to return since, a major sticking point in the long defunct peace process.

A senior State Department official traveling with Blinken from Jordan to Qatar said the U.S. is talking to Israel, U.N. agencies and the International Committee of the Red Cross on creating safe zones within Gaza, where civilians can receive humanitarian aid. It was not clear if the aid would enter from Israel or Egypt.

The official said there appears to be little desire on anyone’s part to unfettered border crossings into Egypt, given the impact on the already restive Sinai and the economic burden, and they don’t want Palestinians who are already refugees to become double refugees. The U.S. focus on Egypt has been on getting Palestinians with dual nationality out through Rafah if they wish. The official spoke on condition of anonymity to discuss private and ongoing diplomatic discussions.

Egyptian officials have long feared that Israel seeks to make their country responsible for Palestinians in Gaza, which Egypt ruled between the 1948 and 1967 Mideast wars. Egypt has joined Israel in its blockade of the Gaza Strip since the Hamas takeover, tightly controlling entry of supplies and the exit of people.

Israel’s evacuation call told Palestinians to move to southern Gaza, raising expectations of a ground assault. A military spokesman said they would be allowed back once the war is over. But with bombardment continuing in south Gaza, the mass movement will likely put pressure on Egypt’s border.

Israel has not detailed its long-term plan for Gaza beyond crushing Hamas, which has ruled there since 2007. Even if displaced are allowed back, it isn’t known what will remain of their homes and economy.

A senior Egyptian security official told The Associated Press that Egypt has taken “unprecedented measures” to prevent a breach to its borders with Gaza. Thousands of security forces have been deployed at the border, he said.

In 2008, Hamas militants blasted through the border fence with Egypt, allowing hundreds of thousands of people to flood into Sinai. The state-run al-Ahram daily reported that Egyptian authorities warned Hamas’ leaders in recent days against any repeat of that.

The official said Egyptian officials have been communicating “around the clock” with Israel, Hamas, the United States and European countries proposing a cease-fire, allowing aid delivery through Rafah and creating “safe zones” inside Gaza. He said there has been no Israeli response. The official spoke on condition of anonymity because he was not allowed to talk to news media.

The Israeli Foreign Ministry said it was unaware of any contacts with Egypt about a cease-fire or humanitarian aid, though such contacts often take place among security officials.

Egypt, which has a peace treaty and close security cooperation with Israel and contacts with Hamas, helped broker cease-fires in previous wars between the two sides.

European Union chief diplomat Josep Borrel on Thursday supported Egypt’s proposal to deliver international aid through Rafah. Egypt has called on countries and aid groups to send supplies to its el-Arish airport in northern Sinai, near Rafah. Jordan and Turkey have already sent shipments. Local aid groups, including the Egyptian Red Crescent, also begun collecting aid and donations.

Israel launched its siege of Gaza in retaliation for Hamas’ incursion Saturday, when militants stormed into southern Israel, massacring hundreds of civilians and soldiers and seizing some 150 hostages. More than 3,000 people have been killed on both sides.

___

Associated Press writer Matthew Lee in Washington contributed to this report.