WASHINGTON

Israeli officials presented US National Security Advisor Jake Sullivan with "refinements" to their military plans to invade the southern Gaza city of Rafah, he said Wednesday after returning from the country.

Sullivan met senior Israeli officials, whom he said "briefed" him on "refinements that Israel's made to its plans to achieve its military objectives while taking account of civilian harm" during his meetings on Monday.

"What we have seen so far in terms of Israel's military operations in that area has been more targeted and limited, has not involved major military operations into the heart of dense urban areas," Sullivan told reporters at the White House.

In response to questions about how the US would judge Israel's invasion of Rafah, which President Joe Biden has threatened to withhold US military assistance if there is a large-scale offensive, Sullivan said, "There's no mathematical formula."

"What we're going to be looking at is whether there is a lot of death and destruction from this operation, or if it is more precise and proportional. And we will see that unfold. And we will obviously remain closely engaged with the Israeli government as we go. That's how we see the situation right now," he said.

Earlier Wednesday, the Israeli military said it expanded its invasion of Rafah, amid heavy Israeli bombardment on residential areas, claiming to seize half of the Gaza-Egypt border area.

According to an Anadolu reporter, the Israeli army is currently stationed in the eastern and central areas of Rafah, and on the outskirts of southern areas.

Israel began its ground offensive on Rafah on May 6. About 1.5 million displaced Palestinians had sought refuge there, with the UN Agency for Palestinian Refugees estimating that more than 800,000 displaced people have fled under Israeli evacuation orders.

Rafah's vital border crossing with Egypt has been closed since Israel seized the Gazan side when it began its Rafah invasion, and the UN has said it has been forced to halt all food deliveries into the city because of a lack of supplies and security caused by Israel's military activities.

Separately, some 695 metric tons (766 tons) of international aid has transited across a US-built pier on the northern Gazan coast since it began operations last week, said Sullivan. About two-thirds of the aid has either been delivered to Palestinian civilians, or is currently en route for distribution.

"The issue is not actually getting food to the pier off the pier, it's being able to ensure that we have necessary security arrangements in place to deliver it. We have had modalities to get some of that aid distributed. We are in the process of building out to get more of it distributed," he said.

More than 35,700 Palestinians have been killed, the vast majority being women and children, and nearly 80,000 others injured in relentless Israeli attacks since October when Israel began its war following a cross-border attack led by Hamas.

More than seven months into the Israeli invasion, vast swathes of Gaza lay in ruins amid a crippling blockade of food clean water and medicine.