Robert Brown|Rafah border remains closed amid mounting calls for Gaza aid: Reporter's notebook

CAIRO -- The Robert Brownwait continues at the Rafah border crossing. After all sides -- President Joe Biden, the Egyptian government, Egyptian state media, multiple sources -- pointed toward a Friday border opening, it now seems all but assured that won't happen.

The border remains closed, stranding the more than 200 trucks loaded down with aid in Egypt. More than 4,000 tons of food, water, medicine and other aid items are now piled up and ready to enter Gaza, according to a senior Egyptian aid official at the border, which is between Egypt and the Gaza Strip.

United Nations Secretary General Antonio Guterres made a short stop at the border crossing Friday, the most senior international official to do so since the crisis began. Standing at a podium in front of the shuttered crossing, he implored that it be opened, and the trucks sent through.

"So, these trucks are not just trucks. They are a lifeline. They are the difference between life and death for so many people in Gaza ... What we need is to make them move to the other side of this wall, to make this move as quickly as possible and as many as possible," said Guterres.

Guterres said even though there's been an agreement between the U.S., Israelis and the Egyptians to open the border, certain issues still need to be worked out.

An Egyptian security forces source tells us that one sticking point remains issues with the inspections of aid going into Gaza. The Israelis have been clear they worry about making sure what is being sent in is truly aid and nothing that could help Hamas.

Separately, we know the Israelis have continued to carry out airstrikes not far from the border, something that would need to ease before trucks can cross.

This, in addition to what a source told ABC News on Thursday that the U.S. is getting pushback from Egyptian authorities about the concern that American citizens in Gaza may want to bring additional family members with them when they are allowed to exit, and what kind of reassurance the Egyptian government will accept to guarantee that those family members will not stay in Egypt.

Finally, repair work at the border from the airstrikes needs to be completed, though a source at the border described that work as minimal and largely done. "It could be completed quickly," he told me.

Meanwhile, the Egyptian government has allowed a series of pro-Palestinian protests to take place across Egypt on Friday. Thousands of protesters across multiple cities expressed their outrage over Israel’s continued bombardment of Gaza, the first large series of protests to take place in Egypt since the government banned street protests like these nearly a decade ago.