A senior U.S. military official shared an update on the temporary pier intended to help deliver humanitarian aid to Gaza in a briefing for Pentagon reporters Thursday.

"We are on track to begin delivery of humanitarian assistance to Gaza from the sea in early May," the military official said.

Once operational, the U.S. expects the pier will be able to handle about 90 trucks a day and then quickly build up to 150 trucks worth of humanitarian aid, the official added.

The official explained how the flow of aid will be transferred via the pier, saying, supplies will be unloaded onto a floating platform located miles off the Gaza shore and then a smaller watercraft carrying five trucks will be offloaded onto the floating pier that will be anchored to the shore.

From there, the trucks will drop off their cargo in a secure area for future distribution and constantly repeat that process, according to the official.

The truck drivers will not be U.S. military personnel but the drivers, from an undisclosed country, will have their own security, according to the official.

The U.S. military has begun to build a temporary pier off the coast of Gaza to help deliver humanitarian aid, the Pentagon's top spokesperson confirmed at a press briefing Thursday.

"We are aware of the significant interest in this important effort and will provide much more information in the very near future as we work alongside the international community to rush aid to the people of Gaza," Maj. Gen. Pat Ryder told reporters.

In the wake of a mortar attack in the general vicinity of where the pier is located near Gaza City earlier Thursday, Ryder said the pier and causeway are being built miles offshore and are "nowhere near mortar range."

The incident "in no way delays our efforts to establish the maritime corridor," Ryder said.

The pier should be ready to off-load humanitarian aid from ships by early May, he said.

-ABC News' Luis Martinez

President Joe Biden and the leaders of 17 other countries -- Argentina, Austria, Brazil, Bulgaria, Canada, Colombia, Denmark, France, Germany, Hungary, Poland, Portugal, Romania, Serbia, Spain, Thailand and the U.K. -- are calling for the release of all hostages held by Hamas in Gaza in a new statement released Thursday.

“The fate of the hostages and the civilian population in Gaza, who are protected under international law, is of international concern," they said in a statement released Thursday. "We emphasize that the deal on the table to release the hostages would bring an immediate and prolonged cease-fire in Gaza, that would facilitate a surge of additional necessary humanitarian assistance to be delivered throughout Gaza, and lead to the credible end of hostilities."

"Gazans would be able to return to their homes and their lands with preparations beforehand to ensure shelter and humanitarian provisions. We strongly support the ongoing mediation efforts in order to bring our people home. We reiterate our call on Hamas to release the hostages, and let us end this crisis so that collectively we can focus our efforts on bringing peace and stability to the region," the statement read.

-ABC News' Justin Ryan Gomez and Michelle Stoddart

The parents of Hersh Goldberg-Polin, who was taken hostage by Hamas more than six months ago, felt a "total mix of emotions" when a new video of their son was released on Wednesday.

"First and foremost, just a huge sense of relief and gratitude to both see him and hear him. Something about that multi-sensory was really overwhelming. He's alive," Jon Polin, his father, said in an interview on "Good Morning America" on Thursday. "Assuming this video is current, which we believe it is, he's alive."

A video released on Wednesday on a Hamas-run Telegram channel showed a man who identified himself as Goldberg-Polin, a 24-year-old American who was captured at the Nova Music Festival on Oct. 7.

In the heavily edited video, the Israeli-American hostage asks Israeli Prime Minister Benjamin Netanyahu and his government to continue working to secure the release of the hostages.

Rachel Goldberg, his mother, said on Thursday she couldn't pay attention to the words her son was saying when she first watched the new video.

"I wasn't even listening to the content, I was just hearing my only son's voice. Seeing him move and try to look into his eyes," she said. "Any parent, anyone, anyone who has parents, can imagine after 201 days, more than half a year of doubt and fear and angst and trauma to have that, it was very bittersweet. And it was truly overwhelming."

Goldberg-Polin's parents in a "GMA" interview in October described their son as a "curious" and a "laid-back person."

Goldberg said at the time that her mantra had become, "Stay strong, survive. Stay strong, survive."

She repeated that mantra on Thursday.

"We love you, stay strong, survive," she said. "And I definitely, you know, more than ever, after seeing him and seeing that he is clearly medically compromised, medically fragile, that is my continued plea to him, to his soul."

-ABC News' Kevin Shalvey

Israel has dramatically increased the flow of humanitarian supplies into Gaza, allowing on average 200 aid trucks a day, with some days as many as 400 trucks getting through, according to a top U.S. official.

Now, the focus needs to move beyond "counting trucks" and instead look to ensure the right supplies are being distributed throughout Gaza, according to David Satterfield, the State Department’s special envoy for Middle East humanitarian issues.

"Our first priority was -- because it had to be -- averting famine," Satterfield told reporters on Tuesday. "But we now need to move on beyond that goal to addressing the true needs: sanitation, availability of medicines, availability of potable water, the specialized care required for these vulnerable populations."

The United Nations this week is conducting a more detailed assessment on the needs for the civilian population, Satterfield said.

He said the U.N. needs more trucks that are cleared by the Israeli military to operate inside Gaza. He also said the Erez crossing between Gaza and Israel and an additional northern crossing must become accessible.

"Our work is focused every day, every hour, on seeing continuous progress made," he said.

-ABC News’ Anne Flaherty