Senior Israeli officials have expressed "deep frustration" with the Biden administration over its decision to pause a weapons shipment to Israel, warning the move could jeopardize hostage negotiations, two sources briefed on the issue told Axios.

Why it matters: The unprecedented move by the Biden administration, first reported by Axios on Sunday, was a way for the U.S. to signal its concern over Israel's plans for a possible ground invasion of Rafah, U.S. officials said.

• "We're going to continue to do what's necessary to ensure that Israel has the means to defend itself. But that said, we are currently reviewing some near-term security assistance shipments in the context of unfolding events in Rafah," Defense Secretary Lloyd Austin testified in a Senate hearing Wednesday.
• The pause has increased tensions between the Biden administration and the Netanyahu government, which have been steadily growing in recent months amid domestic and global fallout from the war in Gaza.

State of play: More than one million displaced Palestinians have been sheltering in Rafah, a city in the southern Gaza Strip that Israel has called Hamas' last military stronghold.

• The Biden administration is opposed to any major ground operation Israel conducts in Rafah that doesn't include a credible plan for protecting civilians.
• On Monday, Israel captured the Palestinian side of the Rafah crossing on the eastern outskirts of the city.
• The White House sees the Rafah operation as "limited" so far and doesn't believe Israel has crossed President Biden's "red line," which could lead to a shift in U.S. policy toward the war in Gaza, U.S. officials told Axios.
• But the officials warned that if the operation broadens or gets out of control — and Israeli forces go into the city of Rafah itself — it will be "a breaking point" for U.S.-Israeli relations.

Behind the scenes: Israeli officials were sent scrambling to get an explanation for the U.S. decision to pause a weapons shipment that included 1,800 2,000-pound bombs and 1,700 500-pound bombs.

• In recent days, after the Israeli government confirmed that the U.S. paused the shipment in the context of Rafah, officials expressed deep frustration to their American counterparts, sources briefed on the issue said.
• The sources said Israel told the Biden administration it was upset not only about the decision to put the shipment on hold, but also about the decision to leak it to the media.

Reality check: Contrary to the Israeli claims about U.S. media leaks, Axios first broke the news of the pause based on information from two Israeli officials.

• "It's rich that some Israeli officials are complaining about 'leaks' when it was Israeli officials who leaked this in the first place," a U.S. official said.

Between the lines: The Israelis told the U.S. they are extremely concerned that — with negotiations ongoing in Cairo — the timing of the move will jeopardize efforts to secure a deal for the release of hostages and a temporary ceasefire, the sources said.

• The Israelis are concerned that Hamas will not move from its positions when it sees the level of U.S. pressure on Israel.
• Israeli officials told the Biden administration that it needs to put pressure on Hamas, not on Israel, and reiterated their expectation that the U.S. will continue to stand with Israel as it fights to defeat Hamas.

What to watch: Austin told the Senate Appropriations Defense subcommittee that the U.S. hasn't made a final decision about what to do with this weapons shipment, but has stressed to Israel its expectations for a possible operation in Rafah.