By Kevin Liptak and Jeremy Diamond, CNN

Washington (CNN) — President Joe Biden said Tuesday Israel’s prime minister needs to change his hardline government and warned support for the country’s military campaign is waning amid heavy bombardment of Gaza.

Speaking to Democratic donors in Washington, Biden said Prime Minister Benjamin Netanyahu had a “tough decision to make.”

“This is the most conservative government in Israel’s history,” Biden said, adding that the Israeli government “doesn’t want a two-state solution.”

Biden said Israel was beginning to lose support around the world, and argued Netanyahu “has to strengthen and change” the Israeli government to find an eventual long-term solution to the Israeli-Palestinian conflict.

The remarks – delivered at an off-camera fundraiser, a venue in which the president has been more freewheeling than his usual White House appearances – amounted to some of Biden’s most candid to date when it comes to his view of the ongoing war. Before the war broke out, Biden had been open in his criticism of Netanyahu’s governing coalition, which includes far-right parties. But he has mostly stood shoulder-to-shoulder with Netanyahu in public since the conflict began, despite mounting criticism of the Israeli campaign.

Now, however, some daylight has been emerging between the United States and Israel as the civilian death toll in Gaza climbs.

In phone calls, Biden has encouraged Netanyahu to do more to avoid civilian casualties, but top administration officials have said there is a “gap” between Israel’s intentions and the realities on the ground.

Speaking Monday evening at a White House Hanukkah reception, Biden acknowledged Israel was in “a tough spot” following the Hamas attack on October 7 and the subsequent war in Gaza. And he alluded to differences with Netanyahu amid the current fighting.

“We’ll continue to provide military assistance to Israel until they get rid of Hamas, but we have to be careful – they have to be careful,” Biden said. “The whole world’s public opinion can shift overnight, we can’t let that happen.”

Biden and Netanyahu have a decades-long relationship that has at times been strained. At the Monday evening reception, Biden said he once gifted Netanyahu a photo and wrote at the top: “I love you but I don’t agree with a damn thing you had to say.”

“It’s about the same today,” Biden said, adding he’d “had my differences with some Israeli leadership.”

Biden administration officials have been pressing their Israeli counterparts in recent weeks to begin planning for what happens in Gaza once the military campaign ends, including insisting on keeping the door open for an eventual Palestinian state.

The US says it would reject any proposal that includes Israeli control over Gaza and has warned against shrinking the Palestinian territory’s boundaries.

The US is also pressuring Israel to open the Kerem Shalom border crossing to allow humanitarian aid trucks to go directly into Gaza on an emergency basis, US officials told CNN.

The Israeli government on Tuesday allowed aid trucks to be inspected at Kerem Shalom for the first time since Hamas’s attack on October 7, but those trucks must still drive back through Egypt before entering Gaza through the Rafah crossing. While the move doubles Israel’s capacity to inspect aid trucks, it does not resolve the bottleneck that is emerging at the Rafah crossing.

Biden raised the issue directly with Netanyahu during their last call last week, the US officials said. National security adviser Jake Sullivan also urged his Israeli counterparts to open up the Israel-Gaza crossing before he arrives in Israel for meetings on Thursday, the officials said.

“Rafah cannot absorb a sufficient amount of aid to meet the needs of the Palestinian people which are only growing as there have been more people displaced,” Sullivan told CNN in a phone interview Tuesday.

“We need the capacity that Kerem Shalom provides – on an emergency basis – to get more food, water, medicine and essentials in to be distributed to Palestinian civilians and we’re putting that quite urgently to the Israeli government to say, ‘We are asking you to do this ASAP because of the nature of the humanitarian situation on the ground,’” he added.

A spokeswoman for the Israeli prime minister’s office declined to comment on the US move. Israel has so far resisted the idea. It cut off all commercial and humanitarian aid traffic from Israel into Gaza since Hamas launched its surprise terrorist attack on October 7 and has vowed to sever all ties with Gaza.