The State Department was tracking the potential for a significant escalation in Israel’s military campaign in Gaza throughout the day but did not have confirmation that the Israel Defense Forces would expand its ground operations until around the time it was announced to the public earlier Friday, according to two U.S. officials.

Officials say the U.S. has been pressuring Israel to adopt a narrower scope for its offensive and take a more incremental approach. One source said that while Israeli forces seem likely to stay on the ground in Gaza for a longer duration this time, if this incursion doesn't spiral, it could be a positive sign that the administration is successfully making its case.

At this hour, there is still no clarity from the U.S. side on whether this is the big ground offensive that's been expected -- or just part of the buildup.

Officials are confident that they can keep up the short windows of calm that have allowed a limited amount of aid to flow into Gaza through the Rafah Gate, but these fall short of the sustained “humanitarian truce” the United Nations is demanding.

But several other delicate negotiations directly involving the U.S. -- including efforts to free the hostages, allow foreign nationals to exit Gaza and create safe spaces inside the enclave -- could be sidelined by a more comprehensive ground assault. Talks with all parties involved press on. Officials acknowledge that the U.S. would have liked to resolve these issues before any escalation, but that Hamas was likely to use its leverage to push off additional military action as long as possible.

-ABC News' Shannon K. Crawford

Doctors Without Borders made an urgent plea for protection of medical centers in Gaza, after the organization said it has lost contact with its members in the region.

In a video post on X, formerly known as Twitter, Avril Benoit, the organization's executive director, said she was very concerned about the patients, staff and civilians who are taking shelter at al-Shifa Hospital.

The Israel Defense Force said Hamas was using the hospital as a shield for its tunnels and ops centers.

"We call for the unequivocal protection of all medical facilities, staff and civilians across the Gaza Strip," she said. "We need an immediate cease-fire now."

UNICEF said it has also lost contact with its employees in Gaza and is "extremely concerned about their safety."

-ABC News' Cindy Smith

When asked whether troops had launched a ground invasion into the Gaza Strip on Friday night, Israel Defense Forces spokesperson Peter Lerner told ABC News, "We are conducting our sweep and clear activities in order to create better conditions for optimal operational conditions on the ground."

"So we are seeking out anti-tank capabilities, we are destroying observation posts and we are engaging the terrorists where we find them on the front lines or in the peripheral of the Gaza Strip," he continued, noting that troops have been "conducting these activities" for "several days" but he can't detail specifics due to "operational concerns."

"We intend on dismantling their capabilities, destroying their government, and making sure they can never use the Gaza Strip as a staging ground against our people again," Lerner added.

The United Nations General Assembly on Friday adopted a resolution calling for an "immediate, durable and sustained humanitarian truce" between Israel and Hamas.

The resolution also demands the "continuous, sufficient and unhindered" provision of supplies and services for civilians in Gaza, as Israel says it is expanding its ground operations in the territory.

Israel's expanding ground assault on Gaza will involve months of painstaking and "very fierce fighting" with Hamas extremists amid conditions "unlike anything that we’ve seen in recent years," retired Army Gen. Robert Abrams predicted on Sunday.

"And simultaneously trying to ensure that the Israelis do not target, unwittingly, the locations on the hostages -- this is going to prove to be a very difficult task," Abrams told ABC "This Week" co-anchor Martha Raddatz. "And we’ll just have to see how their plan plays out here over the coming days."

Abrams, who commanded U.S. troops during America's invasion of Afghanistan and Iraq, went on to say that he believes Israeli forces face a nigh insurmountable challenge in their stated goal to destroy the militant group that launched a terror attack on Israel earlier this month -- while seeking to limit civilian casualties in the Palestinian territory and recover the hundreds of captives Hamas is thought to be holding in Gaza.

"It’s going to be what I would consider nearly impossible to destroy Hamas, to eliminate their capability to do harm to Israel and the Israeli people, while simultaneously protecting what some people have estimated as to be a million Palestinians who are in harm’s way and they can’t get out of harm’s way," Abrams said.

Israel has faced mounting international outcry at the potential humanitarian disaster in the blockaded territory as it carries out its retaliatory operations on the militants.

Abrams said on "This Week" that he thinks "every effort is being made to follow the laws of armed conflict" but acknowledged the "horrific" images being broadcast of the escalating conflict.

"Fundamentally, at the end of this, Martha ... we still have to answer the question: What is the future? Hamas was created as a result of a lack of a separate Palestinian state. A two-state solution, as many people have talked about. That has to be somewhere, when you asked, 'How does this end?' That has to be part of the equation," Abrams said.

-ABC News' Adam Carlson