With a fragile ceasefire between Israel and Hamas in effect, many questions about the reconstruction of the Gaza Strip remain. It may take decades, not years, to rebuild Gaza due to the massive destruction, an expert from the Brookings Institute told ABC News.

Under the ceasefire agreement, the Gaza Strip is set to be redeveloped for the Palestinian people. Jaco Cilliers, an official from United Nations Development Programme, said at a press conference on Tuesday that it had already cleared some 81,000 tons of rubble from the Gaza Strip and was continuing to do so.

However, it is unclear when reconstruction will begin and who will finance the effort, the Brookings Institute expert, Hady Amr, told ABC News.

Amr, the former U.S. representative for Palestinian affairs from 2022 until 2025, said:

"I don't think there's any modern comparison to what's going to need to happen in the Gaza Strip right now. The level of destruction and devastation is just absolutely immense.

"Imagine not just your house was destroyed, your block was destroyed, your neighborhood was destroyed, but 80 to 90% of the universe that you have access to. It's just going to be incredibly difficult for people to just even continue to survive while the reconstruction takes place."

About 83% of all buildings in Gaza City alone were damaged as of Sept. 23, according to the United Nations Satellite Center. About 40% of those buildings were destroyed. Schools, hospitals, as well as water and electricity infrastructure have all been devastated during the two-year war from Israel's extensive military campaign on the Gaza Strip.

Israel has faced heavy criticism and condemnation over its military action in Gaza from humanitarian rights groups and aid groups.

In September, the International Association of Genocide Scholars -- the world's largest group of academic scholars studying the topic -- passed a resolution saying Israel's "policies and actions" in Gaza "meet the legal definition of genocide," established by the U.N. in 1948.

Israel has denied that it is committing a genocide in Gaza and denied claims that it has targeted civilian infrastructure. As part of the ceasefire agreement, Israel has agreed to allow into Gaza higher volumes of much needed aid.

Recovery

Significant amounts of equipment and supplies will be needed to begin recovery. Mona Yacoubian, the director and senior adviser of the Middle East Program at the bipartisan, nonprofit think tank Center for Strategic and International Studies, told ABC News:

"With the rubble and the massive destruction, there is also concern that there are a number of victims, of bodies, that are buried in that rubble -- they would also need to be exhumed."

Before reconstruction can begin, there need to be areas that are safe and cleared of unexploded ordnance, Yacoubian said. Amr echoed this point, noting that removing unexploded ordnance and removing rubble will both be a "massive issue" that could take years.

There needs to be a restoration of services like running water and electricity in the meantime, according to Yacoubian.

"There's going to need to be a massive scale up of life saving assistance just to ensure that people are getting food and medical assistance and also shelter, so perhaps tents, and all the kinds of things that are required."

The ceasefire agreement ensures humanitarian aid can resume entry into Gaza immediately at a larger scale.

The agreement released by the White House said:

"At a minimum, aid quantities will be consistent with what was included in the January 19, 2025, agreement regarding humanitarian aid, including rehabilitation of infrastructure (water, electricity, sewage), rehabilitation of hospitals and bakeries, and entry of necessary equipment to remove rubble and open roads."

Since the ceasefire went into effect on Oct. 10, it's unclear how much additional humanitarian aid has been allowed into Gaza, though Israel has long maintained they have always allowed enough aid into Gaza.

The UN and other international aid organizations have reported they are able to move more freely around Gaza in areas where the IDF has withdrawn, but additional border crossing points have yet to open.

Challenges ahead

Many challenges lie ahead, starting with whether this is really the end of the conflict, according to Amr.

"The central challenges today are ending the war, getting Israel to end its military occupation, and then we need to get to a situation where there can be a security force that comes in to provide basic security. Once that happens, that's when reconstruction can start.

"Freedom of movement of people and goods, that is the central challenge. Palestinians have the skills and knowledge and in fact, much of the Persian Gulf was built with Palestinian knowledge, know-how and manpower. Tens of thousands of Palestinians have long worked in Israel as construction workers.

"It's just a question of getting access to having the basic freedom to import what they need to get going."

Who will pay?

It will take about $70 billion to rebuild Gaza, according to an operational damage and needs assessment conducted jointly by the United Nations, the European Union and the World Bank.

European and Arab nations, Canada and the U.S. appear willing to contribute to the estimated $70 billion needed to rebuild Gaza, the UN official said on Tuesday.

"We've heard very positive news from a number of our partners, including European partners... Canada" regarding their willingness to help, the official, Cillers, told a press conference, adding that there were also discussions with the U.S.

Oil-rich Arab Gulf states will likely be willing to pay for the reconstruction of Gaza, according to Amr and Yacoubian. Egypt could also provide a "logistical base," he noted.

"United Arab Emirates, Qatar, Saudi Arabia, I think, are all poised to potentially fund this. Turkey, I think has a great interest in doing it, but their relations with Israel are at a low point," Amr said.

However, Yacoubian expressed her belief that more progress towards Palestinian statehood needs to be achieved before countries will commit:

"I think that we could certainly see Gulf countries funding it, but they have signaled that they will not fund reconstruction in Gaza in the absence of a longer-term solution to the conflict. And in particular, they are looking to see demonstrated progress on a path toward Palestinian statehood."