The International Court of Justice said it will hold hearings over Israel's attacks on Rafah during the war in Gaza, after South Africa sought new emergency measures as part of its ongoing case accusing Israel of violating the Genocide Convention in its offensive on Gaza.

Hearings will be held on Thursday and Friday in the Hague.

South Africa first brought the case before the ICJ in December alleging Israel violated its obligations in its offensive with regard to Palestinians in the Gaza Strip.

National security adviser Jake Sullivan stressed the U.S. is working "urgently and relentlessly" to get a hostage deal in place, but did not have any major progress to share Monday.

Sullivan noted that he met with the families of American hostages this past Friday, and that "they know how hard the president is working on this."

On where the hostage negotiations stand currently, Sullivan turned to the architect of the Good Friday agreement in Ireland.

"Sen. [George] Mitchell said quite famously, "'Negotiations are 1,000 days of failure and one day of success.' And right now, we're in the former days rather than the latter day," he said.

"[T]here could be a cease-fire tomorrow if Hamas simply released women, wounded and elderly hostages, all innocents. Israel put a forward-leaning proposal on the table for a cease-fire and hostage deal. The world should be calling on Hamas to come back to the table and accept a deal," Sullivan said.

-ABC News' Molly Nagle

The State Department on Monday said it was aware of reports that U.S. doctors were trapped in Gaza, and that it's been working with Israel to reopen the Rafah gate so U.S. citizens and other foreign nationals can leave.

"I can say that we're aware of these reports of U.S. citizen doctors and medical professionals currently unable to leave Gaza," principal deputy spokesman Vedant Patel said. "As I said before, we don't control this border crossing. And this is a incredibly complex situation that has very serious implications for the safety and security of U.S. citizens. But we're continuing to work around the clock with the government of Israel, with the government of Egypt, to work on this issue."

He added, "Rafah is a conduit for the safe departure of foreign nationals, which is why we continue to want to see it get opened as swiftly as possible."

The State Department said it does not have an estimate of Americans still trapped in Gaza, but that it's helped 1,800 U.S. citizens and legal permanent residents to depart Gaza so far.

"Unfortunately, this is not a border crossing the United States controls but we are continuing to work around the clock with the government of Israel, with the government of Egypt on whatever we can do to make sure that Rafah gets open. … We need to see Rafah open as soon as possible," Patel said.

-ABC News' Anne Flaherty

A United Nations worker was killed and another injured after their vehicle was struck in Gaza on Monday, the organization said.

The staff members of the U.N. Department of Safety and Security were traveling to the European Hospital in Rafah when their U.N. vehicle was struck, the U.N. said.

Details on the incident were not immediately available. The U.N. said it is still gathering information.

U.N. Secretary-General António Guterres has called for a full investigation, his spokesperson said.

"Humanitarian workers must be protected," Guterres said on X. "I condemn all attacks on U.N. personnel and reiterate my urgent appeal for an immediate humanitarian ceasefire & the release of all hostages."

More than 190 U.N. staff members have been killed in Gaza since Oct. 7, according to Guterres.

Three U.S. medical professionals remain in Gaza despite warnings from the U.S. State Department that the American government may not be able to get them out later.

Tamer Hassan, a registered nurse, Dr. Jomana Al-Hinti and Dr. Adam Hamawy were the only ones out of a group of 20 American medical professionals who stayed behind to help treat patients.

"They understand that the U.S. embassy may not be able to facilitate their departure in the same manner as we have just effected today," a person with knowledge of the situation told ABC News.

Hamawy released a statement Saturday explaining why he stayed behind.

"We worry that the European Hospital we currently are in will suffer a similar fate of Al-Shifa and Nasser hospitals, where humanitarian workers, patients, and civilians were massacred," he said.

"To my wife, daughters and son, I know it hurts that I am not coming home this weekend, and I am sorry. But I know that you are proud that I am upholding my oath to never leave anyone behind," he added.

The doctors who left Gaza "made their way to safety with assistance from the U.S. Embassy in Jerusalem," a State Department spokesman said.

-ABC News' Anne Flaherty, Nadine Shubailat and Zoe Magee