Secretary of State Tony Blinken told Israeli Prime Minister Netanyahu and Defense Minister Yoav Gallant in Jerusalem on Wednesday that the Biden administration is very concerned about a possible expansion of Israel's military operation into the southern Gazan city of Rafah, an Israeli official and a source briefed on the issue said.

Why it matters: More than 1 million Palestinians — many displaced from elsewhere in Gaza — are concentrated in Rafah and the surrounding areas along the border between Gaza and Egypt.

• The U.S. is concerned that an Israeli Defense Forces operation in the city without evacuating the civilian population to safe areas will lead to mass casualties.
• It also fears that such an operation will push tens of thousands of Palestinians into Egypt. The Egyptian government has already warned the displacement of Palestinians to Egypt would lead to a rupture in its relations with Israel.

Driving the news: Gallant and other Israeli officials have said in recent days that the IDF will expand its ground operation to Rafah to dismantle the Hamas battalions in the city that until now have remained mostly unharmed.

• Blinken on Wednesday met with Netanyahu and Gallant, as well as IDF chief of staff Herzi Halevi, Shin Bet director Ronen Bar and Mossad director David Barnea.

Gallant told Blinken during the meeting that Hamas' response to the hostage deal proposal will push Israel to expand its ground operation in Gaza, a senior Israeli official said.

• "The response was drafted in a way that will make Israel reject it. Hamas' position will lead to the continuation of the war and our forces to enter more places in Gaza soon," Gallant told Blinken.
• Qatari Prime Minister Sheikh Mohammed bin Abdulrahman al-Thani on Tuesday expressed optimism over what he said was Hamas' generally positive response to the hostage deal proposal.
• Hamas said it still demands that any hostage deal include a comprehensive ceasefire that would end the war in Gaza and lead to a reconstruction effort and the lifting of the siege. But Israel has said it won't commit to ending the war as part of any deal.

The big picture: State Department spokesperson Matthew Miller declined to comment, but said in a statement later Wednesday that Netanyahu and Blinken discussed the "importance of increasing the amount of humanitarian assistance reaching displaced civilians throughout Gaza."

• During the meeting, U.S. envoy David Satterfield spoke about the problems in the delivery of humanitarian aid to Gaza and mentioned the protests by Israelis at the Kerem Shalom crossing preventing trucks from entering the enclave. Blinken interjected and told Netanyahu and Gallant that Israel needs to solve this issue as soon as possible, U.S. and Israeli officials said.
• Blinken also expressed concerns about the failures of communication between the IDF and international organizations and insufficient deconfliction, which led to the targeting of UN personnel who were delivering aid, the sources said.

Blinken and Netanyahu also discussed the latest efforts to secure the release of the hostages still being held in Gaza and the U.S. "vision for durable peace and security in the region," Miller said.

• Blinken reiterated the U.S. support for a future Palestinian state and stressed "the urgent need to de-escalate tensions in the West Bank and prevent the conflict from expanding."

Zoom in: The intense fighting in Khan Younis continues to drive thousands of people to Rafah, the UN aid office (OCHA) said on Tuesday. "Most are living in makeshift structures, tents, or out in the open," according to the UN.

• The influx of people in Rafah is putting more pressure on the already strained humanitarian and medical operations in the enclave, OCHA added.
• The UN last week described Rafah as a "pressure cooker of despair."

Zoom out: More than 27,700 Palestinians, the majority of whom are women and children, have been killed since the war started four months ago, according to the Ministry of Health in Hamas-run Gaza.

• The Israeli government has vowed to destroy Hamas following the military group's Oct. 7 attack on Israel that killed some 1,200 people, the majority of whom are civilians, according to Israeli officials.

Go deeper: State Department reviewing options for possible recognition of Palestinian state

Editor's note: This story has been corrected to reflect Blinken's meeting with Netanyahu took place in Jerusalem, not Tel Aviv. It's also been updated with additional details.