Live updates: Follow the latest news on Israel-Gaza
The US is in constant communication with Israel to discuss the possible consequences of a ground invasion of the Gaza Strip, a major military operation that could have widespread outcomes for the entire region.
Israel is amassing troops and weapons outside Gaza and has already conducted limited forays into the Hamas-controlled territory.
But before an all-out invasion, the families of hostages held in Gaza are pleading with Israel to pause and allow more time for negotiations.
The Pentagon, meanwhile, is sending military staff and equipment into the region to protect against attacks from anti-Israel militias, which are expected to increase following an invasion.
White House National Security spokesman John Kirby said on Monday Israel's army and political leadership will make the final decision on the timing and scope of any invasion.
“We are talking to them about all the kinds of consequences, second and third-order effects, that come from making decisions on the battlefield and what that means,” Mr Kirby said.
“We're curious to understand as best we can the how, the aims and the strategy that they're putting into the effort.”
Pentagon press secretary Brig Gen Pat Ryder said Defence Secretary Lloyd Austin was speaking on a near-daily basis to his Israeli equal, Yoav Gallant.
“Those conversations are on what are Israel's defence needs, which we're working urgently to meet,” Brig Gen Ryder said.
“Part of that also is talking about the importance of conducting operations in accordance with the law of war, most notably the protection of civilians.”
He declined to comment on operational timelines for any Israeli invasion but said the Pentagon was well aware of the risks of a ground incursion in terms of anti-Israel groups stepping up attacks.
“We recognise the potential for increased escalation and we want to do everything we need to do to ensure force protection for our troops, while also at the same time to turn in a broader regional conflict,” he said.
The Pentagon has detailed attacks on US forces thought to have been conducted by Iran-backed militias.
A senior US defence official said American military experts were offering assistance to Israeli partners.
"We have an entire generation of US military senior leaders who have experience in counter-terrorism and complex operations, especially in an urban environment like Gaza," the official told reporters.
"And we have consistently made our experts available to provide their best practices and lessons learnt to our Israeli counterparts."
Several US outlets said the Biden administration is pressuring Israel to delay an invasion, but Israel's ambassador to the US, Michael Herzog, denied this.
“Israel is a sovereign nation, and they do not ask us or tell us what to do. They understand the situation. So there is no real pressure," Mr Herzog told CNN on Sunday.
Israeli Prime Minister Benjamin Netanyahu has vowed to eliminate Hamas and Israel's troops could enter Gaza at any moment, but many families are urging him to focus solely on the hostages.
“This should be the top priority, not to destroy Hamas, not to control Gaza and not anything else,” said Noam Alon, the partner of Inbar Haiman, 27, an artist who was one of dozens abducted from a music festival, Reuters reported.
Hamas is holding more than 200 hostages, among them foreign citizens.
On Friday, the group freed two American hostages after mediation by Qatar.
Ten Americans are still unaccounted for, a “handful” of whom are believed to be held in Gaza, Mr Kirby said. Two more Israeli hostages were released on Monday.
Israel has been bombarding the Gaza Strip since October 7, when Hamas gunmen launched a surprise attack on parts of southern Israel, killing 1,400 people and taking more than 200 hostage.
In recent days, it also conducted limited overnight incursions into the besieged territory, intended to gather intelligence, the Israeli army said.
More than two weeks into the daily air strikes on Gaza that have so far killed more than 5,000 Palestinians, according to local tallies, it remains unclear when Israel will launch a full-scale invasion.
The prospects of a full-scale operation have raised fears of the war spreading beyond Gaza and Israel, which could see Iranian-backed groups in the region, such as Hezbollah, escalating a conflict that could spread in the Middle East.
Israel has been trading fire with Hezbollah in southern Lebanon and in recent days has conducted air strikes on the West Bank and Syria, too.
The US has also been advocating for the entry of humanitarian aid to Gaza, home to 2.3 million people.
On Saturday, 20 lorries carrying aid were allowed into the enclave for the first time since the latest conflict broke out. Two additional smaller convoys have since made their way in through Gaza's border with Egypt.
“We know the needs are acute, and we know they're significant, we know that two convoys of trucks is not enough,” Mr Kirby said.